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10 <title>Debian Policy Manual</title>
11 <author><ref id="authors"></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
25 Copyright © 1996,1997,1998 Ian Jackson
26 and Christian Schwarz.
29 This manual is free software; you may redistribute it and/or
30 modify it under the terms of the GNU General Public License
31 as published by the Free Software Foundation; either version
32 2, or (at your option) any later version.
36 This is distributed in the hope that it will be useful, but
37 <em>without any warranty</em>; without even the implied
38 warranty of merchantability or fitness for a particular
39 purpose. See the GNU General Public License for more
44 A copy of the GNU General Public License is available as
45 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
46 distribution or on the World Wide Web at
47 <url id="http://www.gnu.org/copyleft/gpl.html"
48 name="The GNU General Public Licence">. You can also
49 obtain it by writing to the Free Software Foundation, Inc.,
50 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
58 <heading>About this manual</heading>
60 <heading>Scope</heading>
62 This manual describes the policy requirements for the Debian
63 GNU/Linux distribution. This includes the structure and
64 contents of the Debian archive and several design issues of the
65 operating system, as well as technical requirements that
66 each package must satisfy to be included in the
72 This manual also describes Debian policy as it relates to
73 creating Debian packages. It is not a tutorial on how to build
74 packages, nor is it exhaustive where it comes to describing
75 the behavior of the packaging system. Instead, this manual
76 attempts to define the interface to the package management
77 system that the developers have to be conversant with.<footnote>
79 Informally, the criteria used for inclusion is that the
80 material meet one of the following requirements:
81 <taglist compact="compact">
82 <tag>Standard interfaces</tag>
85 The material presented represents an interface to
86 the packaging system that is mandated for use, and
87 is used by, a significant number of packages, and
88 therefore should not be changed without peer
89 review. Package maintainers can then rely on this
90 interfaces not changing, and the package
91 management software authors need to ensure
92 compatibility with these interface
93 definitions. (Control file and changelog file
94 formats are examples.)
97 <tag>Chosen Convention</tag>
100 If there are a number of technically viable choices
101 that can be made, but one needs to select one of
102 these options for inter-operability. The version
103 number format is one example.
107 Please note that these are not mutually exclusive;
108 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 In this manual, the words <em>must</em>, <em>should</em> and
121 <em>may</em>, and the adjectives <em>required</em>,
122 <em>recommended</em> and <em>optional</em>, are used to
123 distinguish the significance of the various guidelines in
124 this policy document. Packages that do not conform to the
125 guidelines denoted by <em>must</em> (or <em>required</em>)
126 will generally not be considered acceptable for the Debian
127 distribution. Non-conformance with guidelines denoted by
128 <em>should</em> (or <em>recommended</em>) will generally be
129 considered a bug, but will not necessarily render a package
130 unsuitable for distribution. Guidelines denoted by
131 <em>may</em> (or <em>optional</em>) are truly optional and
132 adherence is left to the maintainer's discretion.
135 These classifications are roughly equivalent to the bug
136 severities <em>serious</em> (for <em>must</em> or
137 <em>required</em> directive violations), <em>minor</em>,
138 <em>normal</em> or <em>important</em>
139 (for <em>should</em> or <em>recommended</em> directive
140 violations) and <em>wishlist</em> (for <em>optional</em>
142 <p>Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.</p>
147 Much of the information presented in this manual will be
148 useful even when building a package which is to be
149 distributed in some other way or is intended for local use
155 <heading>New versions of this document</heading>
157 The current version of this document is always accessible
158 from the Debian FTP server <ftpsite>ftp.debian.org</ftpsite>
160 <ftppath>/debian/doc/package-developer/policy.txt.gz</ftppath>
161 (also available from the same directory are several other
162 formats: <file>policy.html.tar.gz</file>, <file>policy.pdf.gz</file>
163 and <file>policy.ps.gz</file>) or from the <url
164 id="http://www.debian.org/doc/debian-policy/" name="Debian
165 Policy Manual"> webpage.</p>
168 In addition, this manual is distributed via the Debian package
169 <file>debian-policy</file>.
173 The <tt>debian-policy</tt> package also includes the file
174 <file>upgrading-checklist.txt</file> which indicates policy
175 changes between versions of this document.
180 <heading>Authors and Maintainers</heading>
183 Originally called "Debian GNU/Linux Policy Manual", this
184 manual was initially written in 1996 by Ian Jackson.
185 It was revised on November 27th, 1996 by David A. Morris.
186 Christian Schwarz added new sections on March 15th, 1997,
187 and reworked/restructured it in April-July 1997.
188 Christoph Lameter contributed the "Web Standard".
192 Since September 1998, the responsibility for the contents of
193 this document lies on the debian-policy mailing list. Proposals
194 are discussed there and inserted into policy after a certain
195 consensus is established.
196 <!-- insert shameless policy-process plug here eventually -->
197 The actual editing is done by a group of maintainers that have
198 no editorial powers. These are the current maintainers:
201 <item>Julian Gilbey</item>
202 <item>Branden Robinson</item>
203 <item>Josip Rodin</item>
204 <item>Manoj Srivastava</item>
209 While the authors of this document have tried hard to avoid
210 typos and other errors, these do still occur. If you discover
211 an error in this manual or if you want to give any
212 comments, suggestions, or criticisms please send an email to
213 the Debian Policy List,
214 <email>debian-policy@lists.debian.org</email>, or submit a
215 bug report against the <tt>debian-policy</tt> package.
219 Please do not try to reach the individual authors or maintainers
220 of the Policy Manual regarding changes to the Policy.
226 <heading>The Debian Archive</heading>
228 The Debian GNU/Linux system is maintained and distributed as a
229 collection of <em>packages</em>. Since there are so many of
230 them (currently well over 6000), they are split into
231 <em>sections</em> and given <em>priorities</em> to simplify
232 the handling of them.
235 The effort of the Debian project is to build a free operating
236 system, but not every package we want to make accessible is
237 <em>free</em> in our sense (see the Debian Free Software
238 Guidelines, below), or may be imported/exported without
239 restrictions. Thus, the archive is split into the sections
240 <em>main</em>, <em>non-free</em>, <em>contrib</em>,
241 <em>non-US/main</em>, <em>non-US/non-free</em>, and
242 <em>non-US/contrib</em>. The sections are explained in detail
247 The <em>main</em> and the <em>non-US/main</em> sections
248 together form the <em>Debian GNU/Linux distribution</em>.
252 Packages in the other sections are not considered to be part
253 of the Debian distribution, although we support their use and
254 provide infrastructure for them (such as our bug-tracking
255 system and mailing lists). This Debian Policy Manual applies
256 to these packages as well.</p>
258 <sect id="pkgcopyright">
259 <heading>Package copyright and sections</heading>
261 The aims of this section are:
263 <list compact="compact">
265 <p>to allow us to make as much software available as we
269 <p>to allow us to encourage everyone to write free
273 <p>to allow us to make it easy for people to produce
274 CD-ROMs of our system without violating any licenses,
275 import/export restrictions, or any other laws.</p>
280 <heading>The Debian Free Software Guidelines</heading>
282 The Debian Free Software Guidelines (DFSG) form our
283 definition of `free software'. These are:
285 <tag>Free Redistribution
289 The license of a Debian component may not restrict any
290 party from selling or giving away the software as a
291 component of an aggregate software distribution
292 containing programs from several different
293 sources. The license may not require a royalty or
294 other fee for such sale.
301 The program must include source code, and must allow
302 distribution in source code as well as compiled form.
309 The license must allow modifications and derived
310 works, and must allow them to be distributed under the
311 same terms as the license of the original software.
314 <tag>Integrity of The Author's Source Code
318 The license may restrict source-code from being
319 distributed in modified form <em>only</em> if the
320 license allows the distribution of ``patch files''
321 with the source code for the purpose of modifying the
322 program at build time. The license must explicitly
323 permit distribution of software built from modified
324 source code. The license may require derived works to
325 carry a different name or version number from the
326 original software. (This is a compromise. The Debian
327 Project encourages all authors to not restrict any
328 files, source or binary, from being modified.)
331 <tag>No Discrimination Against Persons or Groups
335 The license must not discriminate against any person
339 <tag>No Discrimination Against Fields of Endeavor
343 The license must not restrict anyone from making use
344 of the program in a specific field of endeavor. For
345 example, it may not restrict the program from being
346 used in a business, or from being used for genetic
350 <tag>Distribution of License
354 The rights attached to the program must apply to all
355 to whom the program is redistributed without the need
356 for execution of an additional license by those
360 <tag>License Must Not Be Specific to Debian
364 The rights attached to the program must not depend on
365 the program's being part of a Debian system. If the
366 program is extracted from Debian and used or
367 distributed without Debian but otherwise within the
368 terms of the program's license, all parties to whom
369 the program is redistributed must have the same
370 rights as those that are granted in conjunction with
374 <tag>License Must Not Contaminate Other Software
378 The license must not place restrictions on other
379 software that is distributed along with the licensed
380 software. For example, the license must not insist
381 that all other programs distributed on the same medium
382 must be free software.
385 <tag>Example Licenses
389 The ``GPL,'' ``BSD,'' and ``Artistic'' licenses are
390 examples of licenses that we consider <em>free</em>.
397 <heading>The main section</heading>
399 Every package in <em>main</em> and <em>non-US/main</em>
400 must comply with the DFSG (Debian Free Software
404 In addition, the packages in <em>main</em>
405 <list compact="compact">
408 must not require a package outside of <em>main</em>
409 for compilation or execution (thus, the package must
410 not declare a "Depends", "Recommends", or
411 "Build-Depends" relationship on a non-<em>main</em>
417 must not be so buggy that we refuse to support them,
423 must meet all policy requirements presented in this
430 Similarly, the packages in <em>non-US/main</em>
431 <list compact="compact">
434 must not require a package outside of <em>main</em>
435 or <em>non-US/main</em> for compilation or
441 must not be so buggy that we refuse to support them,
446 must meet all policy requirements presented in this
454 <heading>The contrib section</heading>
456 Every package in <em>contrib</em> and
457 <em>non-US/contrib</em> must comply with the DFSG.
461 In addition, the packages in <em>contrib</em> and
462 <em>non-US/contrib</em>
463 <list compact="compact">
466 must not be so buggy that we refuse to support them,
472 must meet all policy requirements presented in this
480 Furthermore, packages in <em>contrib</em> must not require
481 a package in a <em>non-US</em> section for compilation or
486 Examples of packages which would be included in
487 <em>contrib</em> or <em>non-US/contrib</em> are:
488 <list compact="compact">
491 free packages which require <em>contrib</em>,
492 <em>non-free</em> packages or packages which are not
493 in our archive at all for compilation or execution,
499 wrapper packages or other sorts of free accessories for
507 <heading>The non-free section</heading>
509 Packages must be placed in <em>non-free</em> or
510 <em>non-US/non-free</em> if they are not compliant with
511 the DFSG or are encumbered by patents or other legal
512 issues that make their distribution problematic.
515 In addition, the packages in <em>non-free</em> and
516 <em>non-US/non-free</em>
517 <list compact="compact">
520 must not be so buggy that we refuse to support them,
526 must meet all policy requirements presented in this
527 manual that it is possible for them to meet.<footnote>
529 It is possible that there are policy
530 requirements which the package is unable to
531 meet, for example, if the source is
532 unavailable. These situations will need to be
533 handled on a case-by-case basis.
543 <heading>The non-US sections</heading>
545 Non-free programs with cryptographic program code need to
546 be stored on the <em>non-us</em> server because of export
547 restrictions of the U.S.
550 Programs which use patented algorithms that have a
551 restrictied license also need to be stored on "non-us",
552 since that is located in a country where it is not allowed
553 to patent algorithms.
556 A package depends on another package which is distributed
557 via the non-us server has to be stored on the non-us
562 <heading>Further copyright considerations</heading>
564 Every package must be accompanied by a verbatim copy of
565 its copyright and distribution license in the file
566 <file>/usr/share/doc/<var>package</var>/copyright</file>
567 (see <ref id="copyrightfile"> for further details).
570 We reserve the right to restrict files from being included
571 anywhere in our archives if
572 <list compact="compact">
575 their use or distribution would break a law,
580 there is an ethical conflict in their distribution or
586 we would have to sign a license for them, or
591 their distribution would conflict with other project
599 Programs whose authors encourage the user to make
600 donations are fine for the main distribution, provided
601 that the authors do not claim that not donating is
602 immoral, unethical, illegal or something similar; in such
603 a case they must go in <em>non-free</em>.</p>
606 Packages whose copyright permission notices (or patent
607 problems) do not even allow redistribution of binaries
608 only, and where no special permission has been obtained,
609 must not be placed on the Debian FTP site and its mirrors
613 Note that under international copyright law (this applies
614 in the United States, too), <em>no</em> distribution or
615 modification of a work is allowed without an explicit
616 notice saying so. Therefore a program without a copyright
617 notice <em>is</em> copyrighted and you may not do anything
618 to it without risking being sued! Likewise if a program
619 has a copyright notice but no statement saying what is
620 permitted then nothing is permitted.</p>
623 Many authors are unaware of the problems that restrictive
624 copyrights (or lack of copyright notices) can cause for
625 the users of their supposedly-free software. It is often
626 worthwhile contacting such authors diplomatically to ask
627 them to modify their license terms. However, this can be a
628 politically difficult thing to do and you should ask for
629 advice on the <tt>debian-legal</tt> mailing list first, as
634 When in doubt about a copyright, send mail to
635 <email>debian-legal@lists.debian.org</email>. Be prepared
636 to provide us with the copyright statement. Software
637 covered by the GPL, public domain software and BSD-like
638 copyrights are safe; be wary of the phrases `commercial
639 use prohibited' and `distribution restricted'.
643 <heading>Subsections</heading>
646 The packages in the sections <em>main</em>,
647 <em>contrib</em> and <em>non-free</em> are grouped further
648 into <em>subsections</em> to simplify handling.
652 The section and subsection for each package should be
653 specified in the package's <tt>Section</tt> control
654 record. However, the maintainer of the Debian archive
655 may override this selection to ensure the consistency of
656 the Debian distribution. The <tt>Section</tt> field
657 should be of the form:
658 <list compact="compact">
661 <em>subsection</em> if the package is in the
662 <em>main</em> section,
667 <em>section/subsection</em> if the package is in
668 the <em>contrib</em> or <em>non-free</em> section,
674 <tt>non-US</tt>, <tt>non-US/contrib</tt> or
675 <tt>non-US/non-free</tt> if the package is in
676 <em>non-US/main</em>, <em>non-US/contrib</em> or
677 <em>non-US/non-free</em> respectively.
684 The Debian archive maintainers provide the authoritative
685 list of subsections. At present, they are:
686 <em>admin</em>, <em>base</em>, <em>comm</em>,
687 <em>contrib</em>, <em>devel</em>, <em>doc</em>,
688 <em>editors</em>, <em>electronics</em>, <em>games</em>,
689 <em>graphics</em>, <em>hamradio</em>,
690 <em>interpreters</em>, <em>libs</em>, <em>mail</em>,
691 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
692 <em>non-US</em>, <em>non-free</em>, <em>oldlibs</em>,
693 <em>otherosfs</em>, <em>science</em>, <em>shells</em>,
694 <em>sound</em>, <em>tex</em>, <em>text</em>,
695 <em>utils</em>, <em>web</em>, <em>x11</em>.
699 <heading>Priorities</heading>
702 Each package should have a <em>priority</em> value, which is
703 included in the package's <em>control record</em>. This
704 information is used by the Debian package management tools
705 to separate high-priority packages from less-important
709 The following <em>priority levels</em> are recognised by the
710 Debian package management tools.
712 <tag><tt>required</tt></tag>
715 Packages which are necessary for the proper
716 functioning of the system. You must not remove these
717 packages or your system may become totally broken and
718 you may not even be able to use <prgn>dpkg</prgn> to
719 put things back. Systems with only the
720 <tt>required</tt> packages are probably unusable, but
721 they do have enough functionality to allow the
722 sysadmin to boot and install more software.</p>
724 <tag><tt>important</tt></tag>
727 Important programs, including those which one would
728 expect to find on any Unix-like system. If the
729 expectation is that an experienced Unix person who
730 found it missing would say `What on earth is going on,
731 where is <prgn>foo</prgn>?', it must be an
732 <tt>important</tt> package.<footnote>
734 This is an important criterion because we are
735 trying to produce, amongst other things, a free
739 Other packages without which the system will not run
740 well or be usable must also have priority
741 <tt>important</tt>. This does
742 <em>not</em> include Emacs, the X Window System, TeX
743 or any other large applications. The
744 <tt>important</tt> packages are just a bare minimum of
745 commonly-expected and necessary tools.</p>
747 <tag><tt>standard</tt></tag>
750 These packages provide a reasonably small but not too
751 limited character-mode system. This is what will be
752 installed by default if the user doesn't select anything
753 else. It doesn't include many large applications.</p>
755 <tag><tt>optional</tt></tag>
758 (In a sense everything that isn't required is
759 optional, but that's not what is meant here.) This is
760 all the software that you might reasonably want to
761 install if you didn't know what it was and don't have
762 specialized requirements. This is a much larger system
763 and includes the X Window System, a full TeX
764 distribution, and many applications. Note that
765 optional packages should not conflict with each other.
768 <tag><tt>extra</tt></tag>
771 This contains all packages that conflict with others
772 with required, important, standard or optional
773 priorities, or are only likely to be useful if you
774 already know what they are or have specialised
781 Packages must not depend on packages with lower priority
782 values (excluding build-time dependencies). In order to
783 ensure this, the priorities of one or more packages may need
789 <heading>Binary packages</heading>
792 The Debian GNU/Linux distribution is based on the Debian
793 package management system, called <prgn>dpkg</prgn>. Thus,
794 all packages in the Debian distribution must be provided
795 in the <tt>.deb</tt> file format.</p>
799 <heading>The package name</heading>
802 Every package must have a name that's unique within the Debian
806 Package names must consist of lower case letters
807 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
808 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
809 They must be at least two characters long and must start
810 with an alphanumeric character.
814 The package name is part of the file name of the
815 <tt>.deb</tt> file and is included in the control field
821 <heading>The maintainer of a package</heading>
823 Every package must have a Debian maintainer (the
824 maintainer may be one person or a group of people
825 reachable from a common email address, such as a mailing
826 list). The maintainer is responsible for ensuring that
827 the package is placed in the appropriate distributions.
831 The maintainer must be specified in the
832 <tt>Maintainer</tt> control field with their correct name
833 and a working email address. If one person maintains
834 several packages, he/she should try to avoid having
835 different forms of their name and email address in
836 the <tt>Maintainer</tt> fields of those packages.
840 If the maintainer of a package quits from the Debian
841 project, "Debian QA Group"
842 <email>packages@qa.debian.org</email> takes over the
843 maintainership of the package until someone else
844 volunteers for that task. These packages are called
845 <em>orphaned packages</em>.<footnote>
847 The detailed procedure for doing this gracefully can
848 be found in the Debian Developer's Reference, either
849 in the <tt>developers-reference</tt> package, or on
850 the Debian FTP server
851 <ftpsite>ftp.debian.org</ftpsite> as
852 <ftppath>/debian/doc/package-developer/developers-reference.txt.gz</ftppath>
854 id="http://www.debian.org/doc/packaging-manuals/developers-reference/"
855 name="Debian Developer's Reference"> webpage.
863 <heading>The description of a package</heading>
866 Every Debian package must have an extended description
867 stored in the appropriate field of the control record.</p>
870 The description should be written so that it gives the
871 system administrator enough information to decide whether
872 to install the package. This description should not just
873 be copied verbatim from the program's documentation.
874 Instructions for configuring or using the package should
875 not be included (that is what installation scripts,
876 manual pages, info files, etc., are for). Copyright
877 statements and other administrivia should not be included
878 either (that is what the copyright file is for).
884 <heading>Dependencies</heading>
887 Every package must specify the dependency information
888 about other packages that are required for the first to
892 For example, a dependency entry must be provided for any
893 shared libraries required by a dynamically-linked executable
894 binary in a package.</p>
897 Packages are not required to declare any dependencies they
898 have on other packages which are marked <tt>Essential</tt>
899 (see below), and should not do so unless they depend on a
900 particular version of that package.</p>
903 Sometimes, a package requires another package to be installed
904 <em>and</em> configured before it can be installed. In this
905 case, you must specify a <tt>Pre-Depends</tt> entry for
909 You should not specify a <tt>Pre-Depends</tt> entry for a
910 package before this has been discussed on the
911 <tt>debian-devel</tt> mailing list and a consensus about
912 doing that has been reached.</p></sect1>
915 <sect1 id="virtual_pkg_sect">
916 <heading>Virtual packages</heading>
919 Sometimes, there are several packages which offer
920 more-or-less the same functionality. In this case, it's
921 useful to define a <em>virtual package</em> whose name
922 describes that common functionality. (The virtual
923 packages only exist logically, not physically; that's why
924 they are called <em>virtual</em>.) The packages with this
925 particular function will then <em>provide</em> the virtual
926 package. Thus, any other package requiring that function
927 can simply depend on the virtual package without having to
928 specify all possible packages individually.</p>
931 All packages should use virtual package names where
932 appropriate, and arrange to create new ones if necessary.
933 They should not use virtual package names (except privately,
934 amongst a cooperating group of packages) unless they have
935 been agreed upon and appear in the list of virtual package
936 names. (See also <ref id="virtual">)</p>
939 The latest version of the authoritative list of virtual
940 package names can be found on
941 <ftpsite>ftp.debian.org</ftpsite> in
942 <ftppath>/debian/doc/package-developer/virtual-package-names-list.txt</ftppath>
943 or your local mirror. In addition, it is included in the
944 <tt>debian-policy</tt> package. The procedure for updating
945 the list is described at the top of the file.</p></sect1>
949 <heading>Base system</heading>
952 The <tt>base system</tt> is a minimum subset of the Debian
953 GNU/Linux system that is installed before everything else
954 on a new system. Thus, only very few packages are allowed
955 to go into the <tt>base</tt> section to keep the required
956 disk usage very small.</p>
959 Most of these packages will have the priority value
960 <tt>required</tt> or at least <tt>important</tt>, and many
961 of them will be tagged <tt>essential</tt> (see below).</p>
968 <heading>Essential packages</heading>
971 Some packages are tagged <tt>essential</tt>. (They have
972 <tt>Essential: yes</tt> in their package control record.)
973 This flag is used for packages that are <em>essential</em>
977 Since these packages cannot be easily removed (one has to
978 specify an extra <em>force option</em> to
979 <prgn>dpkg</prgn> to do so), this flag must not be used
980 unless absolutely necessary. A shared library package
981 must not be tagged <tt>essential</tt>; dependencies will
982 prevent its premature removal, and we need to be able to
983 remove it when it has been superseded.
987 Since dpkg will not prevent upgrading of other packages
988 while an <tt>essential</tt> package is in an unconfigured
989 state, all <tt>essential</tt> packages must supply all of
990 their core functionality even when unconfigured. If the
991 package cannot satisfy this requirement it must not be
992 tagged as essential, and any packages depending on this
993 package must instead have explicit dependency fields as
998 You must not tag any packages <tt>essential</tt> before
999 this has been discussed on the <tt>debian-devel</tt>
1000 mailing list and a consensus about doing that has been
1005 <heading>Tasks</heading>
1008 The Debian install process allows the user to choose from
1009 a number of common tasks which a Debian system can be used to
1010 perform. Selecting a task with <prgn>tasksel</prgn> causes
1011 a set of packages that are useful in performing that task to be
1016 This set of packages is all available packages which have the
1017 name of the selected task in the <tt>Task</tt> field of their
1018 control file. The format of this field is a list of tasks,
1019 separated by commas.
1023 You should not tag any packages as belonging to a task
1024 before this has been discussed on the
1025 <em>debian-devel</em> mailing list and a consensus about
1026 doing that has been reached.
1030 For third parties (and historical reasons), tasksel also
1031 supports constructing tasks based on <em>task
1032 packages</em>. These are packages whose names begin with
1033 <em>task-</em>. Task packages should not be included in the
1038 <sect1 id="maintscripts">
1039 <heading>Maintainer Scripts</heading>
1042 The package installation scripts should avoid producing
1043 output which it is unnecessary for the user to see and
1044 should rely on <prgn>dpkg</prgn> to stave off boredom on
1045 the part of a user installing many packages. This means,
1046 amongst other things, using the <tt>--quiet</tt> option on
1047 <prgn>install-info</prgn>.</p>
1050 Errors which occur during the execution of an installation
1051 script must be checked and the installation must not
1052 continue after an error.
1056 Note that in general <ref id="scripts"> applies to package
1057 maintainer scripts, too.
1061 You should not use <prgn>dpkg-divert</prgn> on a file
1062 belonging to another package without consulting the
1063 maintainer of that package first.
1067 All packages which supply an instance of a common command
1068 name (or, in general, filename) should generally use
1069 <prgn>update-alternatives</prgn>, so that they may be
1070 installed together. If <prgn>update-alternatives</prgn>
1071 is not used, then each package must use
1072 <tt>Conflicts</tt> to ensure that other packages are
1073 de-installed. (In this case, it may be appropriate to
1074 specify a conflict against earlier versions of something
1075 that previously did not use
1076 <prgn>update-alternatives</prgn>; this is an exception to
1077 the usual rule that versioned conflicts should be
1083 <heading>Prompting in maintainer scripts</heading>
1085 Package maintainer scripts may prompt the user if
1086 necessary. Prompting may be accomplished by hand, or by
1087 communicating with a program, such as
1088 <prgn>debconf</prgn>, which conforms to the Debian
1089 Configuration management specification, version 2 or
1090 higher. These are included in the
1091 <file>debconf_specification</file> files in the
1092 <package>debian-policy</package> package.
1093 You may also find this file on the FTP site
1094 <ftpsite>ftp.debian.org</ftpsite> in
1095 <ftppath>/debian/doc/package-developer/debconf_specification.txt.gz</ftppath>
1096 or on your local mirror.<footnote>
1098 4% of Debian packages [see <url
1099 id="http://kitenet.net/programs/debconf/stats/"
1100 name="Debconf stats">] currently use
1101 <package>debconf</package> to prompt the user at
1102 install time, and this number is growing daily. The
1103 benefits of using debconf are briefly explained at
1105 id="http://kitenet.net/doc/debconf-doc/introduction.html"
1106 name="Debconf introduction">; they include
1107 preconfiguration, (mostly) noninteractive
1108 installation, elimination of redundant prompting,
1109 consistency of user interface, etc.
1112 With this increasing number of packages using
1113 <package>debconf</package>, plus the existance of a
1114 nascent second implementation of the Debian
1115 configuration management system
1116 (<package>cdebconf</package>), and the stabilization
1117 of the protocol these things use, the time has
1118 finally come to reflect the use of these things in
1125 Packages which use the Debian Configuration management
1126 specification may contain an additional
1127 <prgn>config</prgn> script and a <tt>templates</tt>
1128 file in their control archive. The <prgn>config</prgn>
1129 script might be run before the <prgn>preinst</prgn>
1130 script, and before the package is unpacked or any of its
1131 dependencies or pre-dependancies are satisfied.
1132 Therefore it must work using only the tools present in
1133 <em>essential</em> packages.<footnote>
1135 <package>Debconf</package> or another tool that
1136 implements the Debian Configuration management
1137 specification will also be installed, and any
1138 versioned dependencies on it will be satisfied
1139 before preconfiguration begins.
1145 Packages should try to minimize the amount of prompting
1146 they need to do, and they should ensure that the user
1147 will only ever be asked each question once. This means
1148 that packages should try to use appropriate shared
1149 configuration files (such as <file>/etc/papersize</file> and
1150 <file>/etc/news/server</file>), and shared
1151 <package>debconf</package> variables rather than each
1152 prompting for their own list of required pieces of
1157 It also means that an upgrade should not ask the same
1158 questions again, unless the user has used <tt>dpkg
1159 --purge</tt> to remove the package's configuration. The
1160 answers to configuration questions should be stored in an
1161 appropriate place in <file>/etc</file> so that the user can
1162 modify them, and how this has been done should be
1166 If a package has a vitally important piece of
1167 information to pass to the user (such as "don't run me
1168 as I am, you must edit the following configuration files
1169 first or you risk your system emitting badly-formatted
1170 messages"), it should display this in the
1171 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1172 prompt the user to hit return to acknowledge the
1173 message. Copyright messages do not count as vitally
1174 important (they belong in
1175 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1176 neither do instructions on how to use a program (these
1177 should be in on-line documentation, where all the users
1181 Any necessary prompting should almost always be confined
1182 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1183 script. If it is done in the <prgn>postinst</prgn>, it
1184 should be protected with a conditional so that
1185 unnecessary prompting doesn't happen if a package's
1186 installation fails and the <prgn>postinst</prgn> is
1187 called with <tt>abort-upgrade</tt>,
1188 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.</p>
1193 <heading>Source packages</heading>
1195 <sect1 id="standardsversion">
1196 <heading>Standards conformance</heading>
1199 In the source package's <tt>Standards-Version</tt> control
1200 field, you should specify the most recent version number
1201 of this policy document with which your package complied
1202 when it was last updated. The current version number is
1207 This information may be used to file bug reports
1208 automatically if your package becomes too much out of
1213 The version number has four components: major and minor
1214 version number and major and minor patch level. When the
1215 standards change in a way that requires every package to
1216 change the major number will be changed. Significant
1217 changes that will require work in many packages will be
1218 signaled by a change to the minor number. The major patch
1219 level will be changed for any change to the meaning of the
1220 standards, however small; the minor patch level will be
1221 changed when only cosmetic, typographical or other edits
1222 are made which neither change the meaning of the document
1223 nor affect the contents of packages.</p>
1226 Thus only the first three components of the policy version
1227 are significant in the <em>Standards-Version</em> control
1228 field, and so either these three components or the all
1229 four components may be specified.<footnote>
1231 In the past, people specified the full version number
1232 in the Standards-Version field, for example `2.3.0.0'.
1233 Since minor patch-level changes don't introduce new
1234 policy, it was thought it would be better to relax
1235 policy and only require the first 3 components to be
1236 specified, in this example `2.3.0'. All four
1237 components may still be used if someone wishes to do
1244 You should regularly, and especially if your package has
1245 become out of date, check for the newest Policy Manual
1246 available and update your package, if necessary. When your
1247 package complies with the new standards you should update the
1248 <tt>Standards-Version</tt> source package field and
1249 release it.<footnote>
1251 See the file <file>upgrading-checklist</file> for
1252 information about policy which has changed between
1253 different versions of this document.
1261 <heading>Package relationships</heading>
1264 Source packages should specify which binary packages they
1265 require to be installed or not to be installed in order to
1266 build correctly. For example, if building a package
1267 requires a certain compiler, then the compiler should be
1268 specified as a build-time dependency.
1272 It is not necessary to explicitly specify build-time
1273 relationships on a minimal set of packages that are always
1274 needed to compile, link and put in a Debian package a
1275 standard "Hello World!" program written in C or C++. The
1276 required packages are called <em>build-essential</em>, and
1277 an informational list can be found in
1278 <file>/usr/share/doc/build-essential/list</file> (which is
1279 contained in the <tt>build-essential</tt>
1282 <list compact="compact">
1284 <p>This allows maintaining the list separately
1285 from the policy documents (the list does not
1286 need the kind of control that the policy
1292 Having a separate package allows one to install
1293 the build-essential packages on a machine, as
1294 well as allowing other packages such as tasks to
1295 require installation of the build-essential
1296 packages using the depends relation.
1301 The separate package allows bug reports against
1302 the list to be categorized separately from
1303 the policy management process in the BTS.
1313 When specifying the set of build-time dependencies, one
1314 should list only those packages explicitly required by the
1315 build. It is not necessary to list packages which are
1316 required merely because some other package in the list of
1317 build-time dependencies depends on them.<footnote>
1319 The reason for this is that dependencies change, and
1320 you should list all those packages, and <em>only</em>
1321 those packages that <em>you</em> need directly. What
1322 others need is their business. For example, if you
1323 only link against <file>libimlib</file>, you will need to
1324 build-depend on <package>libimlib2-dev</package> but
1325 not against any <tt>libjpeg*</tt> packages, even
1326 though <tt>libimlib2-dev</tt> currently depends on
1327 them: installation of <package>libimlib2-dev</package>
1328 will automatically ensure that all of its run-time
1329 dependencies are satisfied.
1335 If build-time dependencies are specified, it must be
1336 possible to build the package and produce working binaries
1337 on a system with only essential and build-essential
1338 packages installed and also those required to satisfy the
1339 build-time relationships (including any implied
1340 relationships). In particular, this means that version
1341 clauses should be used rigorously in build-time
1342 relationships so that one cannot produce bad or
1343 inconsistently configured packages when the relationships
1344 are properly satisfied.
1348 <heading>Changes to the upstream sources</heading>
1351 If changes to the source code are made that are not
1352 specific to the needs of the Debian system, they should be
1353 sent to the upstream authors in whatever form they prefer
1354 so as to be included in the upstream version of the
1358 If you need to configure the package differently for
1359 Debian or for Linux, and the upstream source doesn't
1360 provide a way to do so, you should add such configuration
1361 facilities (for example, a new <prgn>autoconf</prgn> test
1362 or <tt>#define</tt>) and send the patch to the upstream
1363 authors, with the default set to the way they originally
1364 had it. You can then easily override the default in your
1365 <file>debian/rules</file> or wherever is appropriate.</p>
1368 You should make sure that the <prgn>configure</prgn> utility
1369 detects the correct architecture specification string
1370 (refer to <ref id="arch-spec"> for details).</p>
1373 If you need to edit a <prgn>Makefile</prgn> where
1374 GNU-style <prgn>configure</prgn> scripts are used, you
1375 should edit the <file>.in</file> files rather than editing the
1376 <prgn>Makefile</prgn> directly. This allows the user to
1377 reconfigure the package if necessary. You should
1378 <em>not</em> configure the package and edit the generated
1379 <prgn>Makefile</prgn>! This makes it impossible for
1380 someone else to later reconfigure the package.</p>
1383 You should document your changes and updates to the source
1384 package properly in the <file>debian/changelog</file> file.
1385 For more information, please see <ref id="changelogs">.
1391 <heading>Error trapping in makefiles</heading>
1394 When <prgn>make</prgn> invokes a command in a makefile
1395 (including your package's upstream makefiles and
1396 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1397 means that <prgn>sh</prgn>'s usual bad error handling
1398 properties apply: if you include a miniature script as one
1399 of the commands in your makefile you'll find that if you
1400 don't do anything about it then errors are not detected
1401 and <prgn>make</prgn> will blithely continue after
1405 Every time you put more than one shell command (this
1406 includes using a loop) in a makefile command you
1407 must make sure that errors are trapped. For
1408 simple compound commands, such as changing directory and
1409 then running a program, using <tt>&&</tt> rather
1410 than semicolon as a command separator is sufficient. For
1411 more complex commands including most loops and
1412 conditionals you should include a separate <tt>set -e</tt>
1413 command at the start of every makefile command that's
1414 actually one of these miniature shell scripts.</p></sect1>
1418 <heading>Obsolete constructs and libraries</heading>
1421 The include file <tt><varargs.h></tt> is
1422 provided to support end-users compiling very old software;
1423 the library <tt>libtermcap</tt> is provided to support the
1424 execution of software which has been linked against it
1425 (either old programs or those such as Netscape which are
1426 only available in binary form).</p>
1429 Debian packages should be patched to use
1430 <tt><stdarg.h></tt> and <tt>ncurses</tt>
1437 <chapt id="controlfields"><heading>Control files and their fields</heading>
1440 Many of the tools in the package management suite manipulate
1441 data represented in a common format, known as <em>control
1442 data</em>. The data is often stored in <em>control
1443 files</em>. Binary and source packages have control files,
1444 and the <file>.changes</file> files which control the installation
1445 of uploaded files are also in control file format.
1446 <prgn>Dpkg</prgn>'s internal databases are in a similar
1450 <sect id="controlsyntax"><heading>Syntax of control files</heading>
1453 A control file consists of one or more paragraphs of fields.
1454 The paragraphs are separated by blank lines. Some control
1455 files allow only one paragraph; others allow several, in
1456 which case each paragraph usually refers to a different
1457 package. (For example, in source packages, the first
1458 paragraph refers to the source package, and later paragraphs
1459 refer to binary packages generated from the source.)
1463 Each paragraph consists of a series of data fields; each
1464 field consists of the field name, followed by a colon and
1465 then the data/value associated with that field. It ends at
1466 the end of the line. Horizontal whitespace (spaces and
1467 tabs) may occur immediately before or after the value and is
1468 ignored there; it is conventional to put a single space
1469 after the colon. For example, a field might be:
1470 <example compact="compact">
1473 the field name is <tt>Package</tt> and the field value
1478 Some fields' values may span several lines; in this case
1479 each continuation line <em>must</em> start with a space or
1480 tab. Any trailing spaces or tabs at the end of individual
1481 lines of a field value are ignored.
1485 Except where otherwise stated only a single line of data is
1486 allowed and whitespace is not significant in a field body.
1487 Whitespace must not appear inside names (of packages,
1488 architectures, files or anything else) or version numbers,
1489 or between the characters of multi-character version
1494 Field names are not case-sensitive, but it is usual to
1495 capitalize the field names using mixed case as shown below.
1499 Blank lines, or lines consisting only of spaces and tabs,
1500 are not allowed within field values or between fields - that
1501 would mean a new paragraph.
1506 <sect><heading>List of fields</heading>
1508 This list here is not supposed to be exhaustive. Most fields
1509 are dealt with elsewhere in this document.
1511 <sect1 id="f-Package"><heading><tt>Package</tt>
1515 The name of the binary package. Package names consist of
1516 lower case letters (<tt>a-z</tt>), digits (<tt>0-9</tt>),
1517 plus (<tt>+</tt>) and minus (<tt>-</tt>) signs, and
1518 periods (<tt>.</tt>).
1522 They must be at least two characters long and must start
1523 with an alphanumeric character. The use of lowercase
1524 package names is required unless the package you're
1525 building (or referring to, in other fields) is already
1526 using uppercase characters.</p>
1529 <sect1 id="f-Version"><heading><tt>Version</tt>
1533 This lists the source or binary package's version number -
1534 see <ref id="versions">.
1540 id="f-Standards-Version"><heading><tt>Standards-Version</tt>
1544 The most recent version of the standards (the policy
1545 manual and associated texts) with which the package
1546 complies. This is updated manually when editing the
1547 source package to conform to newer standards; it can
1548 sometimes be used to tell when a package needs attention.
1549 Its format is described above; see
1550 <ref id="standardsversion">.
1555 <sect1 id="f-Distribution"><heading><tt>Distribution</tt>
1559 In a <file>.changes</file> file or parsed changelog output
1560 this contains the (space-separated) name(s) of the
1561 distribution(s) where this version of the package should
1562 be installed. Valid distributions are determined by the
1563 archive maintainers.<footnote>
1564 Current distribution names are:
1565 <taglist compact="compact">
1566 <tag><em>stable</em></tag>
1569 This is the current `released' version of Debian
1570 GNU/Linux. Once the distribution is
1571 <em>stable</em> only security fixes and other
1572 major bug fixes are allowed. When changes are
1573 made to this distribution, the release number is
1574 increased (for example: 2.2r1 becomes 2.2r2 then
1579 <tag><em>unstable</em></tag>
1582 This distribution value refers to the
1583 <em>developmental</em> part of the Debian
1584 distribution tree. New packages, new upstream
1585 versions of packages and bug fixes go into the
1586 <em>unstable</em> directory tree. Download from
1587 this distribution at your own risk.
1591 <tag><em>testing</em></tag>
1594 This distribution value refers to the
1595 <em>testing</em> part of the Debian distribution
1596 tree. It receives its packages from the
1597 unstable distribution after a short time lag to
1598 ensure that there are no major issues with the
1599 unstable packages. It is less prone to breakage
1600 than unstable, but still risky. It is not
1601 possible to upload packages directly to
1606 <tag><em>frozen</em></tag>
1609 From time to time, the <em>testing</em>
1610 distribution enters a state of `code-freeze' in
1611 anticipation of release as a <em>stable</em>
1612 version. During this period of testing only
1613 fixes for existing or newly-discovered bugs will
1614 be allowed. The exact details of this stage are
1615 determined by the Release Manager.
1619 <tag><em>experimental</em></tag>
1622 The packages with this distribution value are
1623 deemed by their maintainers to be high
1624 risk. Oftentimes they represent early beta or
1625 developmental packages from various sources that
1626 the maintainers want people to try, but are not
1627 ready to be a part of the other parts of the
1628 Debian distribution tree. Download at your own
1634 You should list <em>all</em> distributions that the
1635 package should be installed into.
1644 <chapt id="versions"><heading>Version numbering</heading>
1647 Every package has a version number recorded in its
1648 <tt>Version</tt> control file field.
1652 The package management system imposes an ordering on version
1653 numbers, so that it can tell whether packages are being up- or
1654 downgraded and so that package system front end applications
1655 can tell whether a package it finds available is newer than
1656 the one installed on the system. The version number format
1657 has the most significant parts (as far as comparison is
1658 concerned) at the beginning.
1662 The version number format is:
1663 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
1667 The three components here are:
1669 <tag><var>epoch</var></tag>
1672 This is a single (generally small) unsigned integer. It
1673 may be omitted, in which case zero is assumed. If it is
1674 omitted then the <var>upstream_version</var> may not
1679 It is provided to allow mistakes in the version numbers
1680 of older versions of a package, and also a package's
1681 previous version numbering schemes, to be left behind.
1685 <tag><var>upstream_version</var></tag>
1688 This is the main part of the version number. It is
1689 usually the version number of the original (`upstream')
1690 package from which the <file>.deb</file> file has been made,
1691 if this is applicable. Usually this will be in the same
1692 format as that specified by the upstream author(s);
1693 however, it may need to be reformatted to fit into the
1694 package management system's format and comparison
1699 The comparison behavior of the package management system
1700 with respect to the <var>upstream_version</var> is
1701 described below. The <var>upstream_version</var>
1702 portion of the version number is mandatory.
1706 The <var>upstream_version</var> may contain only
1707 alphanumerics<footnote>
1708 <p>Alphanumerics are <tt>A-Za-z0-9</tt> only.</p>
1710 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
1711 <tt>:</tt> (full stop, plus, hyphen, colon) and should
1712 start with a digit. If there is no
1713 <var>debian_revision</var> then hyphens are not allowed;
1714 if there is no <var>epoch</var> then colons are not
1718 <tag><var>debian_revision</var></tag>
1721 This part of the version number specifies the version of
1722 the Debian package based on the upstream version. It
1723 may contain only alphanumerics and the characters
1724 <tt>+</tt> and <tt>.</tt> (plus and full stop) and is
1725 compared in the same way as the
1726 <var>upstream_version</var> is.
1730 It is optional; if it isn't present then the
1731 <var>upstream_version</var> may not contain a hyphen.
1732 This format represents the case where a piece of
1733 software was written specifically to be turned into a
1734 Debian package, and so there is only one `debianization'
1735 of it and therefore no revision indication is required.
1739 It is conventional to restart the
1740 <var>debian_revision</var> at <tt>1</tt> each time the
1741 <var>upstream_version</var> is increased.
1745 The package management system will break the version
1746 number apart at the last hyphen in the string (if there
1747 is one) to determine the <var>upstream_version</var> and
1748 <var>debian_revision</var>. The absence of a
1749 <var>debian_revision</var> compares earlier than the
1750 presence of one (but note that the
1751 <var>debian_revision</var> is the least significant part
1752 of the version number).
1759 The <var>upstream_version</var> and <var>debian_revision</var>
1760 parts are compared by the package management system using the
1765 The strings are compared from left to right.
1769 First the initial part of each string consisting entirely of
1770 non-digit characters is determined. These two parts (one of
1771 which may be empty) are compared lexically. If a difference
1772 is found it is returned. The lexical comparison is a
1773 comparison of ASCII values modified so that all the letters
1774 sort earlier than all the non-letters.
1778 Then the initial part of the remainder of each string which
1779 consists entirely of digit characters is determined. The
1780 numerical values of these two parts are compared, and any
1781 difference found is returned as the result of the comparison.
1782 For these purposes an empty string (which can only occur at
1783 the end of one or both version strings being compared) counts
1788 These two steps (comparing and removing initial non-digit
1789 strings and initial digit strings) are repeated until a
1790 difference is found or both strings are exhausted.
1794 Note that the purpose of epochs is to allow us to leave behind
1795 mistakes in version numbering, and to cope with situations
1796 where the version numbering scheme changes. It is
1797 <em>not</em> intended to cope with version numbers containing
1798 strings of letters which the package management system cannot
1799 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
1800 silly orderings (the author of this manual has heard of a
1801 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
1802 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
1803 <tt>2</tt> and so forth).
1807 If an upstream package has problematic version numbers they
1808 should be converted to a sane form for use in the
1809 <tt>Version</tt> field.
1813 <heading>Version numbers based on dates</heading>
1815 In general, Debian packages should use the same version
1816 numbers as the upstream sources.</p>
1819 However, in some cases where the upstream version number is
1820 based on a date (e.g., a development `snapshot' release) the
1821 package management system cannot handle these version
1822 numbers without epochs. For example, dpkg will consider
1823 `96May01' to be greater than `96Dec24'.</p>
1826 To prevent having to use epochs for every new upstream
1827 version, the version number should be changed to the
1828 following format in such cases: `19960501', `19961224'. It
1829 is up to the maintainer whether he/she wants to bother the
1830 upstream maintainer to change the version numbers upstream,
1834 Note that other version formats based on dates which are
1835 parsed correctly by the package management system should
1836 <em>not</em> be changed.</p>
1839 Native Debian packages (i.e., packages which have been
1840 written especially for Debian) whose version numbers include
1841 dates should always use the `YYYYMMDD' format.</p>
1845 <chapt id="miscellaneous"><heading>Packaging Considerations</heading>
1847 <sect id="timestamps"><heading>Time Stamps</heading>
1849 Maintainers should preserve the modification times of the
1850 upstream source files in a package, as far as is reasonably
1853 The rationale is that there is some information conveyed
1854 by knowing the age of the file, for example, you could
1855 recognize that some documentation is very old by looking
1856 at the modification time, so it would be nice if the
1857 modification time of the upstream source would be
1864 <sect id="debianrules"><heading><file>debian/rules</file> - the
1865 main building script</heading>
1868 This file must be an executable makefile, and contains the
1869 package-specific recipes for compiling the package and
1870 building binary package(s) from the source.
1874 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1875 so that it can be invoked by saying its name rather than
1876 invoking <prgn>make</prgn> explicitly.
1880 Since an interactive <file>debian/rules</file> script makes it
1881 impossible to auto-compile that package and also makes it
1882 hard for other people to reproduce the same binary
1883 package, all <em>required targets</em> MUST be
1884 non-interactive. At a minimum, required targets are the
1885 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1886 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1887 <em>binary-indep</em>, and <em>build</em>. It also follows
1888 that any target that these targets depend on must also be
1893 The required and optional targets are as follows:
1895 <tag><tt>build</tt>, <tt>build-arch</tt> (optional),
1896 <tt>build-indep</tt> (optional)</tag>
1899 The <tt>build</tt> target should perform all
1900 non-interactive configuration and compilation of the
1901 package. If a package has an interactive pre-build
1902 configuration routine, the Debianized source package
1903 must either be built after this has taken place (so
1904 that the binary package can be built without rerunning
1905 the configuration) or the configuration routine
1906 modified to become non-interactive. (The latter is
1907 preferable if there are architecture-specific features
1908 detected by the configuration routine.)
1912 For some packages, notably ones where the same
1913 source tree is compiled in different ways to produce
1914 two binary packages, the <tt>build</tt> target
1915 does not make much sense. For these packages it is
1916 good enough to provide two (or more) targets
1917 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1918 for each of the ways of building the package, and a
1919 <tt>build</tt> target that does nothing. The
1920 <tt>binary</tt> target will have to build the
1921 package in each of the possible ways and make the
1922 binary package out of each.
1926 The <tt>build</tt> target must not do anything
1927 that might require root privilege.
1931 The <tt>build</tt> target may need to run the
1932 <tt>clean</tt> target first - see below.
1936 When a package has a configuration and build routine
1937 which takes a long time, or when the makefiles are
1938 poorly designed, or when <tt>build</tt> needs to
1939 run <tt>clean</tt> first, it is a good idea to
1940 <tt>touch build</tt> when the build process is
1941 complete. This will ensure that if <tt>debian/rules
1942 build</tt> is run again it will not rebuild the whole
1945 Another common way to do this is for <tt>build</tt>
1946 to depend on <prgn>build-stamp</prgn> and to do
1947 nothing else, and for the <prgn>build-stamp</prgn>
1948 target to do the building and to <tt>touch
1949 build-stamp</tt> on completion. This is
1950 especially useful if the build routine creates a
1951 file or directory called <tt>build</tt>; in such a
1952 case, <tt>build</tt> will need to be listed as
1953 a phony target (i.e., as a dependency of the
1954 <tt>.PHONY</tt> target). See the documentation of
1955 <prgn>make</prgn> for more information on phony
1962 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1963 <tt>binary-indep</tt>
1967 The <tt>binary</tt> target must be all that is
1968 necessary for the user to build the binary package(s)
1969 produced from this source package. All of these
1970 targets are required to be non-interactive. It is
1971 split into two parts: <prgn>binary-arch</prgn> builds
1972 the binary packages which are specific to a particular
1973 architecture, and <tt>binary-indep</tt> builds
1974 those which are not.
1977 <tt>binary</tt> may be (and commonly is) a target with
1978 no commands which simply depends on
1979 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1982 Both <tt>binary-*</tt> targets should depend on the
1983 <tt>build</tt> target, or on the appropriate
1984 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1985 provided, so that the package is built if it has not
1986 been already. It should then create the relevant
1987 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1988 make their control files and <prgn>dpkg-deb</prgn> to
1989 build them and place them in the parent of the top
1994 Both the <tt>binary-arch</tt> and
1995 <tt>binary-indep</tt> targets <em>must</em> exist.
1996 If one of them has nothing to do (which will always be
1997 the case if the source generates only a single binary
1998 package, whether architecture-dependent or not), it
1999 must still exist and must always succeed.
2003 The <tt>binary</tt> targets must be invoked as
2006 The <prgn>fakeroot</prgn> package often allows one
2007 to build a package correctly even without being
2014 <tag><tt>clean</tt></tag>
2017 This must undo any effects that the <tt>build</tt>
2018 and <tt>binary</tt> targets may have had, except
2019 that it should leave alone any output files created in
2020 the parent directory by a run of a <tt>binary</tt>
2021 target. This target must be non-interactive.
2025 If a <tt>build</tt> file is touched at the end of
2026 the <tt>build</tt> target, as suggested above, it
2027 should be removed as the first action that
2028 <tt>clean</tt> performs, so that running
2029 <tt>build</tt> again after an interrupted
2030 <tt>clean</tt> doesn't think that everything is
2035 The <tt>clean</tt> target may need to be
2036 invoked as root if <tt>binary</tt> has been
2037 invoked since the last <tt>clean</tt>, or if
2038 <tt>build</tt> has been invoked as root (since
2039 <tt>build</tt> may create directories, for
2044 <tag><tt>get-orig-source</tt> (optional)</tag>
2047 This target fetches the most recent version of the
2048 original source package from a canonical archive site
2049 (via FTP or WWW, for example), does any necessary
2050 rearrangement to turn it into the original source
2051 tar file format described below, and leaves it in the
2056 This target may be invoked in any directory, and
2057 should take care to clean up any temporary files it
2062 This target is optional, but providing it if
2063 possible is a good idea.
2069 The <tt>build</tt>, <tt>binary</tt> and
2070 <tt>clean</tt> targets must be invoked with the current
2071 directory being the package's top-level directory.
2076 Additional targets may exist in <file>debian/rules</file>,
2077 either as published or undocumented interfaces or for the
2078 package's internal use.
2082 The architectures we build on and build for are determined
2083 by <prgn>make</prgn> variables using the utility
2084 <prgn>dpkg-architecture</prgn>. You can determine the
2085 Debian architecture and the GNU style architecture
2086 specification string for the build machine (the machine type
2087 we are building on) as well as for the host machine (the
2088 machine type we are building for). Here is a list of
2089 supported <prgn>make</prgn> variables:
2090 <list compact="compact">
2092 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
2095 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2096 specification string)</p>
2099 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of
2100 <tt>DEB_*_GNU_TYPE</tt>)</p>
2103 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2104 <tt>DEB_*_GNU_TYPE</tt>)</p>
2106 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2107 the build machine or <tt>HOST</tt> for specification of the
2112 Backward compatibility can be provided in the rules file
2113 by setting the needed variables to suitable default
2114 values; please refer to the documentation of
2115 <prgn>dpkg-architecture</prgn> for details.
2119 It is important to understand that the <tt>DEB_*_ARCH</tt>
2120 string only determines which Debian architecture we are
2121 building on or for. It should not be used to get the CPU
2122 or system information; the GNU style variables should be
2127 <sect id="dpkgchangelog"><heading><file>debian/changelog</file>
2131 This file records the changes to the Debian-specific parts of the
2134 Though there is nothing stopping an author who is also
2135 the Debian maintainer from using it for all their
2136 changes, it will have to be renamed if the Debian and
2137 upstream maintainers become different people. In such a
2138 case, however, it might be better to maintain the
2139 package as a non-native package.
2145 It has a special format which allows the package building
2146 tools to discover which version of the package is being
2147 built and find out other release-specific information.
2151 That format is a series of entries like this:
2152 <example compact="compact">
2153 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
2155 <p>[optional blank line(s), stripped]</p>
2157 * <var>change details</var>
2158 <var>more change details</var>
2160 <p>[blank line(s), included in output of dpkg-parsechangelog]</p>
2162 * <var>even more change details</var>
2164 <p>[optional blank line(s), stripped]</p>
2166 -- <var>maintainer name</var> <<var>email
2167 address</var>><var>[two spaces]</var> <var>date</var>
2172 <var>package</var> and <var>version</var> are the source
2173 package name and version number.
2177 <var>distribution(s)</var> lists the distributions where
2178 this version should be installed when it is uploaded - it
2179 is copied to the <tt>Distribution</tt> field in the
2180 <file>.changes</file> file. See <ref id="f-Distribution">.
2184 <var>urgency</var> is the value for the <tt>Urgency</tt>
2185 field in the <file>.changes</file> file for the upload. It is
2186 not possible to specify an urgency containing commas; commas
2187 are used to separate
2188 <tt><var>keyword</var>=<var>value</var></tt> settings in the
2189 <prgn>dpkg</prgn> changelog format (though there is
2190 currently only one useful <var>keyword</var>,
2191 <tt>urgency</tt>).<footnote>
2193 Recognised urgency values are <tt>low</tt>,
2194 <tt>medium</tt>, <tt>high</tt> and <tt>emergency</tt>.
2195 They have an effect on how quickly a package will be
2196 considered for inclusion into the <tt>testing</tt>
2197 distribution, and give an indication of the importance
2198 of any fixes included in this upload.
2204 The change details may in fact be any series of lines
2205 starting with at least two spaces, but conventionally each
2206 change starts with an asterisk and a separating space and
2207 continuation lines are indented so as to bring them in
2208 line with the start of the text above. Blank lines may be
2209 used here to separate groups of changes, if desired.
2213 If this upload resolves bugs recorded in the Bug Tracking
2214 System (BTS), they may be automatically closed on the
2215 inclusion of this package into the Debian archive by
2216 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
2217 in the change details.<footnote>
2219 To be precise, the string should match the following
2220 Perl regular expression:
2222 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
2224 Then all of the bug numbers listed will be closed by the
2225 archive maintenance script (<prgn>katie</prgn>), or in
2226 the case of an NMU, marked as fixed.
2232 The maintainer name and email address used in the changelog
2233 should be the details of the person uploading <em>this</em>
2234 version. They are <em>not</em> necessarily those of the
2235 usual package maintainer. The information here will be
2236 copied to the <tt>Changed-By</tt> field in the
2237 <tt>.changes</tt> file, and then later used to send an
2238 acknowledgement when the upload has been installed.
2242 The <var>date</var> should be in RFC822 format<footnote>
2244 This is generated by the <prgn>822-date</prgn>
2247 </footnote>; it should include the time zone specified
2248 numerically, with the time zone name or abbreviation
2249 optionally present as a comment in parentheses.
2253 The first `title' line with the package name should start
2254 at the left hand margin; the `trailer' line with the
2255 maintainer and date details should be preceded by exactly
2256 one space. The maintainer details and the date must be
2257 separated by exactly two spaces.
2260 <sect1><heading>Defining alternative changelog formats</heading>
2263 It is possible to use a different format to the standard
2264 one, by providing a parser for the format you wish to
2268 A changelog parser must not interact with the user at
2274 <sect id="srcsubstvars"><heading><file>debian/substvars</file>
2275 and variable substitutions </heading>
2278 When <prgn>dpkg-gencontrol</prgn>,
2279 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2280 generate control files they perform variable substitutions
2281 on their output just before writing it. Variable
2282 substitutions have the form <tt>${<var>variable</var>}</tt>.
2283 The optional file <file>debian/substvars</file> contains
2284 variable substitutions to be used; variables can also be set
2285 directly from <file>debian/rules</file> using the <tt>-V</tt>
2286 option to the source packaging commands, and certain
2287 predefined variables are also available.
2291 The <file>debian/substvars</file> file is usually generated and
2292 modified dynamically by <file>debian/rules</file> targets; in
2293 this case it must be removed by the <tt>clean</tt>
2298 See <manref name="dpkg-source" section="1"> for full
2299 details about source variable substitutions, including the
2300 format of <file>debian/substvars</file>.</p>
2303 <sect id="debianfiles"><heading><file>debian/files</file>
2307 This file is not a permanent part of the source tree; it
2308 is used while building packages to record which files are
2309 being generated. <prgn>dpkg-genchanges</prgn> uses it
2310 when it generates a <file>.changes</file> file.
2314 It should not exist in a shipped source package, and so it
2315 (and any backup files or temporary files such as
2316 <file>files.new</file><footnote>
2318 <file>files.new</file> is used as a temporary file by
2319 <prgn>dpkg-gencontrol</prgn> and
2320 <prgn>dpkg-distaddfile</prgn> - they write a new
2321 version of <tt>files</tt> here before renaming it,
2322 to avoid leaving a corrupted copy if an error
2325 </footnote>) should be removed by the
2326 <tt>clean</tt> target. It may also be wise to
2327 ensure a fresh start by emptying or removing it at the
2328 start of the <tt>binary</tt> target.
2332 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2333 package, it adds an entry to <file>debian/files</file> for the
2334 <file>.deb</file> file that will be created when <tt>dpkg-deb
2335 --build</tt> is run for that binary package. So for most
2336 packages all that needs to be done with this file is to
2337 delete it in the <tt>clean</tt> target.
2341 If a package upload includes files besides the source
2342 package and any binary packages whose control files were
2343 made with <prgn>dpkg-gencontrol</prgn> then they should be
2344 placed in the parent of the package's top-level directory
2345 and <prgn>dpkg-distaddfile</prgn> should be called to add
2346 the file to the list in <file>debian/files</file>.</p>
2349 <sect id="restrictions"><heading>Restrictions on objects in source packages
2353 The source package may not contain any hard links<footnote>
2355 This is not currently detected when building source
2356 packages, but only when extracting
2360 Hard links may be permitted at some point in the
2361 future, but would require a fair amount of
2364 </footnote>, device special files, sockets or setuid or
2365 setgid files.<footnote>
2367 Setgid directories are allowed.
2372 <sect id="descriptions"><heading>Descriptions of packages - the
2373 <tt>Description</tt> field </heading>
2376 The description is intended to describe the program to a user
2377 who has never met it before so that they know whether they
2378 want to install it. It should also give information about the
2379 significant dependencies and conflicts between this package
2380 and others, so that the user knows why these dependencies and
2381 conflicts have been declared.
2384 <sect1><heading>Notes about writing descriptions
2388 The single line synopsis should be kept brief - certainly
2389 under 80 characters.
2393 Do not include the package name in the synopsis line. The
2394 display software knows how to display this already, and you
2395 do not need to state it. Remember that in many situations
2396 the user may only see the synopsis line - make it as
2397 informative as you can.
2401 Do not try to continue the single line synopsis into the
2402 extended description. This will not work correctly when
2403 the full description is displayed, and makes no sense
2404 where only the summary (the single line synopsis) is
2409 The extended description should describe what the package
2410 does and how it relates to the rest of the system (in terms
2411 of, for example, which subsystem it is which part of).
2415 The description field needs to make sense to anyone, even
2416 people who have no idea about any of the things the
2417 package deals with.<footnote>
2419 The blurb that comes with a program in its
2420 announcements and/or <prgn>README</prgn> files is
2421 rarely suitable for use in a description. It is
2422 usually aimed at people who are already in the
2423 community where the package is used.
2429 Put important information first, both in the synopsis and
2430 extended description. Sometimes only the first part of the
2431 synopsis or of the description will be displayed. You can
2432 assume that there will usually be a way to see the whole
2433 extended description.
2437 You may include information about dependencies and so forth
2438 in the extended description, if you wish.
2442 Do not use tab characters. Their effect is not predictable.
2450 <chapt id="maintainerscripts"><heading>Package maintainer scripts
2451 and installation procedure
2454 <sect><heading>Introduction to package maintainer scripts
2458 It is possible to supply scripts as part of a package which
2459 the package management system will run for you when your
2460 package is installed, upgraded or removed.
2464 These scripts are the files <prgn>preinst</prgn>,
2465 <prgn>postinst</prgn>, <prgn>prerm</prgn> and <prgn>postrm</prgn> in the
2466 control area of the package. They must be proper executable
2467 files; if they are scripts (which is recommended), they must
2468 start with the usual <tt>#!</tt> convention. They should be
2469 readable and executable by anyone, and not world-writable.
2473 The package management system looks at the exit status from
2474 these scripts. It is important that they exit with a
2475 non-zero status if there is an error, so that the package
2476 management system can stop its processing. For shell
2477 scripts this means that you <em>almost always</em> need to
2478 use <tt>set -e</tt> (this is usually true when writing shell
2479 scripts, in fact). It is also important, of course, that
2480 they don't exit with a non-zero status if everything went
2485 When a package is upgraded a combination of the scripts from
2486 the old and new packages is called during the upgrade
2487 procedure. If your scripts are going to be at all
2488 complicated you need to be aware of this, and may need to
2489 check the arguments to your scripts.
2493 Broadly speaking the <prgn>preinst</prgn> is called before
2494 (a particular version of) a package is installed, and the
2495 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
2496 before (a version of) a package is removed and the
2497 <prgn>postrm</prgn> afterwards.
2501 Programs called from maintainer scripts should not normally
2502 have a path prepended to them. Before installation is
2503 started, the package management system checks to see if the
2504 programs <prgn>ldconfig</prgn>,
2505 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
2506 and <prgn>update-rc.d</prgn> can be found via the
2507 <tt>PATH</tt> environment variable. Those programs, and any
2508 other program that one would expect to be on the
2509 <tt>PATH</tt>, should thus be invoked without an absolute
2510 pathname. Maintainer scripts should also not reset the
2511 <tt>PATH</tt>, though they might choose to modify it by
2512 prepending or appending package-specific directories. These
2513 considerations really apply to all shell scripts.</p>
2517 <heading>Maintainer scripts Idempotency</heading>
2520 It is necessary for the error recovery procedures that the
2521 scripts be idempotent. This means that if it is run
2522 successfully, and then it is called again, it doesn't bomb
2523 out or cause any harm, but just ensures that everything is
2524 the way it ought to be. If the first call failed, or
2525 aborted half way through for some reason, the second call
2526 should merely do the things that were left undone the first
2527 time, if any, and exit with a success status if everything
2530 This is so that if an error occurs, the user interrupts
2531 <prgn>dpkg</prgn> or some other unforeseen circumstance
2532 happens you don't leave the user with a badly-broken
2533 package when <prgn>dpkg</prgn> attempts to repeat the
2541 <heading>Controlling terminal for maintainer scripts</heading>
2544 The maintainer scripts are guaranteed to run with a
2545 controlling terminal and can interact with the user.
2546 If they need to prompt for passwords, do full-screen
2547 interaction or something similar you should do these
2548 things to and from <file>/dev/tty</file>, since
2549 <prgn>dpkg</prgn> will at some point redirect scripts'
2550 standard input and output so that it can log the
2551 installation process. Likewise, because these scripts
2552 may be executed with standard output redirected into a
2553 pipe for logging purposes, Perl scripts should set
2554 unbuffered output by setting <tt>$|=1</tt> so that the
2555 output is printed immediately rather than being
2560 Each script should return a zero exit status for
2561 success, or a nonzero one for failure.
2565 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
2570 <list compact="compact">
2572 <p><var>new-preinst</var> <tt>install</tt></p>
2575 <p><var>new-preinst</var> <tt>install</tt>
2576 <var>old-version</var></p>
2579 <p><var>new-preinst</var> <tt>upgrade</tt>
2580 <var>old-version</var></p>
2583 <p><var>old-preinst</var> <tt>abort-upgrade</tt>
2584 <var>new-version</var>
2590 <list compact="compact">
2592 <p><var>postinst</var> <tt>configure</tt>
2593 <var>most-recently-configured-version</var></p>
2596 <p><var>old-postinst</var> <tt>abort-upgrade</tt>
2597 <var>new-version</var></p>
2600 <p><var>conflictor's-postinst</var> <tt>abort-remove</tt>
2601 <tt>in-favour</tt> <var>package</var>
2602 <var>new-version</var></p>
2606 <var>deconfigured's-postinst</var>
2607 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
2608 <var>failed-install-package</var> <var>version</var>
2609 <tt>removing</tt> <var>conflicting-package</var>
2616 <list compact="compact">
2618 <p><var>prerm</var> <tt>remove</tt></p>
2621 <p><var>old-prerm</var> <tt>upgrade</tt>
2622 <var>new-version</var></p>
2625 <p><var>new-prerm</var> <tt>failed-upgrade</tt>
2626 <var>old-version</var></p>
2629 <p><var>conflictor's-prerm</var> <tt>remove</tt>
2630 <tt>in-favour</tt> <var>package</var>
2631 <var>new-version</var></p>
2635 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
2636 <tt>in-favour</tt> <var>package-being-installed</var>
2637 <var>version</var> <tt>removing</tt>
2638 <var>conflicting-package</var>
2645 <list compact="compact">
2647 <p><var>postrm</var> <tt>remove</tt></p>
2650 <p><var>postrm</var> <tt>purge</tt></p>
2654 <var>old-postrm</var> <tt>upgrade</tt>
2655 <var>new-version</var></p>
2658 <p><var>new-postrm</var> <tt>failed-upgrade</tt>
2659 <var>old-version</var></p>
2662 <p><var>new-postrm</var> <tt>abort-install</tt></p>
2665 <p><var>new-postrm</var> <tt>abort-install</tt>
2666 <var>old-version</var></p>
2669 <p><var>new-postrm</var> <tt>abort-upgrade</tt>
2670 <var>old-version</var></p>
2674 <var>disappearer's-postrm</var> <tt>disappear</tt>
2675 <var>overwriter</var>
2676 <var>overwriter-version</var></p></item>
2681 <sect id="unpackphase"><heading>Details of unpack phase of
2682 installation or upgrade
2686 The procedure on installation/upgrade/overwrite/disappear
2687 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
2688 stage of <tt>dpkg --install</tt>) is as follows. In each
2689 case, if a major error occurs (unless listed below) the
2690 actions are, in general, run backwards - this means that the
2691 maintainer scripts are run with different arguments in
2692 reverse order. These are the `error unwind' calls listed
2700 <p>If a version of the package is already
2702 <example compact="compact">
2703 <var>old-prerm</var> upgrade <var>new-version</var>
2708 If the script runs but exits with a non-zero
2709 exit status, <prgn>dpkg</prgn> will attempt:
2710 <example compact="compact">
2711 <var>new-prerm</var> failed-upgrade <var>old-version</var>
2713 Error unwind, for both the above cases:
2714 <example compact="compact">
2715 <var>old-postinst</var> abort-upgrade <var>new-version</var>
2723 <p>If a `conflicting' package is being removed at the same time:
2727 If any packages depended on that conflicting
2728 package and <tt>--auto-deconfigure</tt> is
2729 specified, call, for each such package:
2730 <example compact="compact">
2731 <var>deconfigured's-prerm</var> deconfigure \
2732 in-favour <var>package-being-installed</var> <var>version</var> \
2733 removing <var>conflicting-package</var> <var>version</var>
2736 <example compact="compact">
2737 <var>deconfigured's-postinst</var> abort-deconfigure \
2738 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
2739 removing <var>conflicting-package</var> <var>version</var>
2741 The deconfigured packages are marked as
2742 requiring configuration, so that if
2743 <tt>--install</tt> is used they will be
2744 configured again if possible.</p>
2747 <p>To prepare for removal of the conflicting package, call:
2748 <example compact="compact">
2749 <var>conflictor's-prerm</var> remove \
2750 in-favour <var>package</var> <var>new-version</var>
2753 <example compact="compact">
2754 <var>conflictor's-postinst</var> abort-remove \
2755 in-favour <var>package</var> <var>new-version</var>
2766 <p>If the package is being upgraded, call:
2767 <example compact="compact">
2768 <var>new-preinst</var> upgrade <var>old-version</var>
2773 Otherwise, if the package had some configuration
2774 files from a previous version installed (i.e., it
2775 is in the `configuration files only' state):
2776 <example compact="compact">
2777 <var>new-preinst</var> install <var>old-version</var>
2781 <p>Otherwise (i.e., the package was completely purged):
2782 <example compact="compact">
2783 <var>new-preinst</var> install
2785 Error unwind actions, respectively:
2786 <example compact="compact">
2787 <var>new-postrm</var> abort-upgrade <var>old-version</var>
2788 <var>new-postrm</var> abort-install <var>old-version</var>
2789 <var>new-postrm</var> abort-install
2798 The new package's files are unpacked, overwriting any
2799 that may be on the system already, for example any
2800 from the old version of the same package or from
2801 another package. Backups of the old files are kept
2802 temporarily, and if anything goes wrong the package
2803 management system will attempt to put them back as
2804 part of the error unwind.
2808 It is an error for a package to contains files which
2809 are on the system in another package, unless
2810 <tt>Replaces</tt> is used (see <ref id="replaces">).
2812 The following paragraph is not currently the case:
2813 Currently the <tt>- - force-overwrite</tt> flag is
2814 enabled, downgrading it to a warning, but this may not
2820 It is a more serious error for a package to contain a
2821 plain file or other kind of non-directory where another
2822 package has a directory (again, unless
2823 <tt>Replaces</tt> is used). This error can be
2824 overridden if desired using
2825 <tt>--force-overwrite-dir</tt>, but this is not
2830 Packages which overwrite each other's files produce
2831 behavior which, though deterministic, is hard for the
2832 system administrator to understand. It can easily
2833 lead to `missing' programs if, for example, a package
2834 is installed which overwrites a file from another
2835 package, and is then removed again.<footnote>
2837 Part of the problem is due to what is arguably a
2838 bug in <prgn>dpkg</prgn>.
2844 A directory will never be replaced by a symbolic link
2845 to a directory or vice versa; instead, the existing
2846 state (symlink or not) will be left alone and
2847 <prgn>dpkg</prgn> will follow the symlink if there is
2855 <p>If the package is being upgraded, call
2856 <example compact="compact">
2857 <var>old-postrm</var> upgrade <var>new-version</var>
2862 <p>If this fails, <prgn>dpkg</prgn> will attempt:
2863 <example compact="compact">
2864 <var>new-postrm</var> failed-upgrade <var>old-version</var>
2866 Error unwind, for both cases:
2867 <example compact="compact">
2868 <var>old-preinst</var> abort-upgrade <var>new-version</var>
2875 This is the point of no return - if
2876 <prgn>dpkg</prgn> gets this far, it won't back off
2877 past this point if an error occurs. This will
2878 leave the package in a fairly bad state, which
2879 will require a successful re-installation to clear
2880 up, but it's when <prgn>dpkg</prgn> starts doing
2881 things that are irreversible.
2886 Any files which were in the old version of the package
2887 but not in the new are removed.</p>
2890 <p>The new file list replaces the old.</p>
2893 <p>The new maintainer scripts replace the old.</p>
2897 <p>Any packages all of whose files have been overwritten during the
2898 installation, and which aren't required for
2899 dependencies, are considered to have been removed.
2900 For each such package
2903 <p><prgn>dpkg</prgn> calls:
2904 <example compact="compact">
2905 <var>disappearer's-postrm</var> disappear \
2906 <var>overwriter</var> <var>overwriter-version</var>
2911 <p>The package's maintainer scripts are removed.
2916 It is noted in the status database as being in a
2917 sane state, namely not installed (any conffiles
2918 it may have are ignored, rather than being
2919 removed by <prgn>dpkg</prgn>). Note that
2920 disappearing packages do not have their prerm
2921 called, because <prgn>dpkg</prgn> doesn't know
2922 in advance that the package is going to
2931 Any files in the package we're unpacking that are also
2932 listed in the file lists of other packages are removed
2933 from those lists. (This will lobotomize the file list
2934 of the `conflicting' package if there is one.)
2939 The backup files made during installation, above, are
2946 The new package's status is now sane, and recorded as
2951 Here is another point of no return - if the
2952 conflicting package's removal fails we do not unwind
2953 the rest of the installation; the conflicting package
2954 is left in a half-removed limbo.
2960 If there was a conflicting package we go and do the
2961 removal actions (described below), starting with the
2962 removal of the conflicting package's files (any that
2963 are also in the package being installed have already
2964 been removed from the conflicting package's file list,
2965 and so do not get removed now).
2972 <sect id="configdetails"><heading>Details of configuration</heading>
2975 When we configure a package (this happens with <tt>dpkg
2976 --install</tt> and <tt>dpkg --configure</tt>), we first
2977 update any <tt>conffile</tt>s and then call:
2978 <example compact="compact">
2979 <var>postinst</var> configure <var>most-recently-configured-version</var>
2984 No attempt is made to unwind after errors during
2989 If there is no most recently configured version
2990 <prgn>dpkg</prgn> will pass a null argument; older versions
2991 of dpkg may pass <tt><unknown></tt> (including the
2992 angle brackets) in this case. Even older ones do not pass a
2993 second argument at all, under any circumstances.
2997 <sect id="removedetails"><heading>Details of removal and/or
2998 configuration purging</heading>
3004 <example compact="compact">
3005 <var>prerm</var> remove
3011 The package's files are removed (except <tt>conffile</tt>s).
3016 <example compact="compact">
3017 <var>postrm</var> remove
3023 All the maintainer scripts except the <prgn>postrm</prgn>
3028 If we aren't purging the package we stop here. Note
3029 that packages which have no <prgn>postrm</prgn> and no
3030 <tt>conffile</tt>s are automatically purged when
3031 removed, as there is no difference except for the
3032 <prgn>dpkg</prgn> status.</p>
3036 The <tt>conffile</tt>s and any backup files
3037 (<tt>~</tt>-files, <tt>#*#</tt> files,
3038 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3043 <example compact="compact">
3044 <var>postrm</var> purge
3049 <p>The package's file list is removed.</p>
3052 No attempt is made to unwind after errors during
3059 <chapt id="relationships"><heading>Declaring relationships between
3063 Packages can declare in their control file that they have
3064 certain relationships to other packages - for example, that
3065 they may not be installed at the same time as certain other
3066 packages, and/or that they depend on the presence of others,
3067 or that they should overwrite files in certain other packages
3072 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3073 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3074 <tt>Conflicts</tt>, <tt>Provides</tt> and <tt>Replaces</tt>
3075 control file fields.
3079 Source packages may declare relationships to binary packages,
3080 saying that they require certain binary packages to be
3081 installed or absent at the time of building the package.
3085 This is done using the <tt>Build-Depends</tt>,
3086 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
3087 <tt>Build-Conflicts-Indep</tt> control file fields.
3090 <sect id="depsyntax"><heading>Syntax of relationship fields
3094 These fields all have a uniform syntax. They are a list of
3095 package names separated by commas.
3099 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3100 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3101 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3102 control file fields of the package, which declare
3103 dependencies on other packages, the package names listed may
3104 also include lists of alternative package names, separated
3105 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3106 if any one of the alternative packages is installed, that
3107 part of the dependency is considered to be satisfied.
3111 All of the fields except for <tt>Provides</tt> may restrict
3112 their applicability to particular versions of each named
3113 package. This is done in parentheses after each individual
3114 package name; the parentheses should contain a relation from
3115 the list below followed by a version number, in the format
3116 described in <ref id="versions">.
3120 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3121 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3122 strictly earlier, earlier or equal, exactly equal, later or
3123 equal and strictly later, respectively. The deprecated
3124 forms <tt><</tt> and <tt>></tt> were used to mean
3125 earlier/later or equal, rather than strictly earlier/later,
3126 so they should not appear in new packages (though
3127 <prgn>dpkg</prgn> still supports them).
3131 Whitespace may appear at any point in the version
3132 specification subject to the rules in <ref
3133 id="controlsyntax">, and must appear where it's necessary to
3134 disambiguate; it is not otherwise significant. For
3135 consistency and in case of future changes to
3136 <prgn>dpkg</prgn> it is recommended that a single space be
3137 used after a version relationship and before a version
3138 number; it is also conventional to put a single space after
3139 each comma, on either side of each vertical bar, and before
3140 each open parenthesis.
3144 For example, a list of dependencies might appear as:
3145 <example compact="compact">
3148 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3153 All fields that specify build-time relationships
3154 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3155 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3156 may be restricted to a certain set of architectures. This
3157 is indicated in brackets after each individual package name and
3158 the optional version specification. The brackets enclose a
3159 list of Debian architecture names separated by whitespace.
3160 Exclamation marks may be prepended to each of the names.
3161 (It is not permitted for some names to be prepended with
3162 exclamation marks and others not.) If the current Debian
3163 host architecture is not in this list and there are no
3164 exclamation marks in the list, or it is in the list with a
3165 prepended exclamation mark, the package name and the
3166 associated version specification are ignored completely for
3167 the purposes of defining the relationships.
3172 <example compact="compact">
3174 Build-Depends-Indep: texinfo
3175 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3176 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3181 Note that the binary package relationship fields such as
3182 <tt>Depends</tt> appear in one of the binary package
3183 sections of the control file, whereas the build-time
3184 relationships such as <tt>Build-Depends</tt> appear in the
3185 source package section of the control file (which is the
3191 <heading>Binary Dependencies - <tt>Depends</tt>,
3192 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3193 <tt>Pre-Depends</tt>
3197 These five fields are used to declare a dependency
3198 relationship by one package on another. Except for
3199 <tt>Enhances</tt>, they appear in the depending (binary)
3200 package's control file. (<tt>Enhances</tt> appears in the
3201 recommending package's control file.)
3205 A <tt>Depends</tt> field takes effect <em>only</em> when a
3206 package is to be configured. It does not prevent a package
3207 being on the system in an unconfigured state while its
3208 dependencies are unsatisfied, and it is possible to replace
3209 a package whose dependencies are satisfied and which is
3210 properly installed with a different version whose
3211 dependencies are not and cannot be satisfied; when this is
3212 done the depending package will be left unconfigured (since
3213 attempts to configure it will give errors) and will not
3214 function properly. If it is necessary, a
3215 <tt>Pre-Depends</tt> field can be used, which has a partial
3216 effect even when a package is being unpacked, as explained
3217 in detail below. (The other three dependency fields,
3218 <tt>Recommends</tt>, <tt>Suggests</tt> and
3219 <tt>Enhances</tt>, are only used by the various front-ends
3220 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3224 For this reason packages in an installation run are usually
3225 all unpacked first and all configured later; this gives
3226 later versions of packages with dependencies on later
3227 versions of other packages the opportunity to have their
3228 dependencies satisfied.
3232 The <tt>Depends</tt> field thus allows package maintainers
3233 to impose an order in which packages should be configured.
3237 The meaning of the five dependency fields is as follows:
3239 <tag><tt>Depends</tt></tag>
3242 This declares an absolute dependency. A package will
3243 not be configured unless all of the packages listed in
3244 its <tt>Depends</tt> field have been correctly
3249 The <tt>Depends</tt> field should be used if the
3250 depended-on package is required for the depending
3251 package to provide a significant amount of
3255 The <tt>Depends</tt> field should also be used if the
3256 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
3257 <prgn>postrm</prgn> scripts require the package to be
3258 present in order to run. Note, however, that the
3259 <prgn>postrm</prgn> cannot rely on any non-essential
3260 packages to be present during the <tt>purge</tt>
3264 <tag><tt>Recommends</tt></tag>
3266 <p>This declares a strong, but not absolute, dependency.
3270 The <tt>Recommends</tt> field should list packages
3271 that would be found together with this one in all but
3272 unusual installations.</p>
3275 <tag><tt>Suggests</tt></tag>
3278 This is used to declare that one package may be more
3279 useful with one or more others. Using this field
3280 tells the packaging system and the user that the
3281 listed packages are related to this one and can
3282 perhaps enhance its usefulness, but that installing
3283 this one without them is perfectly reasonable.
3287 <tag><tt>Enhances</tt></tag>
3290 This field is similar to Suggests but works in the
3291 opposite direction. It is used to declare that a
3292 package can enhance the functionality of another
3297 <tag><tt>Pre-Depends</tt></tag>
3300 This field is like <tt>Depends</tt>, except that it
3301 also forces <prgn>dpkg</prgn> to complete installation
3302 of the packages named before even starting the
3303 installation of the package which declares the
3304 pre-dependency, as follows:
3308 When a package declaring a pre-dependency is about to
3309 be <em>unpacked</em> the pre-dependency can be
3310 satisfied if the depended-on package is either fully
3311 configured, <em>or even if</em> the depended-on
3312 package(s) are only unpacked or half-configured,
3313 provided that they have been configured correctly at
3314 some point in the past (and not removed or partially
3315 removed since). In this case, both the
3316 previously-configured and currently unpacked or
3317 half-configured versions must satisfy any version
3318 clause in the <tt>Pre-Depends</tt> field.
3322 When the package declaring a pre-dependency is about
3323 to be <em>configured</em>, the pre-dependency will be
3324 treated as a normal <tt>Depends</tt>, that is, it will
3325 be considered satisfied only if the depended-on
3326 package has been correctly configured.
3330 <tt>Pre-Depends</tt> should be used sparingly,
3331 preferably only by packages whose premature upgrade or
3332 installation would hamper the ability of the system to
3333 continue with any upgrade that might be in progress.
3337 <tt>Pre-Depends</tt> are also required if the
3338 <prgn>preinst</prgn> script depends on the named
3339 package. It is best to avoid this situation if
3345 When selecting which level of dependency to use you should
3346 consider how important the depended-on package is to the
3347 functionality of the one declaring the dependency. Some
3348 packages are composed of components of varying degrees of
3349 importance. Such a package should list using
3350 <tt>Depends</tt> the package(s) which are required by the
3351 more important components. The other components'
3352 requirements may be mentioned as Suggestions or
3353 Recommendations, as appropriate to the components' relative
3358 <sect id="conflicts"><heading>Conflicting binary packages -
3359 <tt>Conflicts</tt></heading>
3362 When one binary package declares a conflict with another
3363 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
3364 refuse to allow them to be installed on the system at the
3369 If one package is to be installed, the other must be removed
3370 first - if the package being installed is marked as
3371 replacing (see <ref id="replaces">) the one on the system,
3372 or the one on the system is marked as deselected, or both
3373 packages are marked <tt>Essential</tt>, then
3374 <prgn>dpkg</prgn> will automatically remove the package
3375 which is causing the conflict, otherwise it will halt the
3376 installation of the new package with an error. This
3377 mechanism is specifically designed to produce an error when
3378 the installed package is <tt>Essential</tt>, but the new
3383 A package will not cause a conflict merely because its
3384 configuration files are still installed; it must be at least
3389 A special exception is made for packages which declare a
3390 conflict with their own package name, or with a virtual
3391 package which they provide (see below): this does not
3392 prevent their installation, and allows a package to conflict
3393 with others providing a replacement for it. You use this
3394 feature when you want the package in question to be the only
3395 package providing some feature.
3399 A <tt>Conflicts</tt> entry should almost never have an
3400 `earlier than' version clause. This would prevent
3401 <prgn>dpkg</prgn> from upgrading or installing the package
3402 which declared such a conflict until the upgrade or removal
3403 of the conflicted-with package had been completed.
3407 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
3411 As well as the names of actual (`concrete') packages, the
3412 package relationship fields <tt>Depends</tt>,
3413 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3414 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
3415 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3416 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
3417 may mention `virtual packages'.
3421 A <em>virtual package</em> is one which appears in the
3422 <tt>Provides</tt> control file field of another package.
3423 The effect is as if the package(s) which provide a
3424 particular virtual package name had been listed by name
3425 everywhere the virtual package name appears. (See also <ref
3426 id="virtual_pkg_sect">)
3430 If there are both concrete and virtual packages of the same
3431 name, then the dependency may be satisfied (or the conflict
3432 caused) by either the concrete package with the name in
3433 question or any other concrete package which provides the
3434 virtual package with the name in question. This is so that,
3435 for example, supposing we have
3436 <example compact="compact">
3440 and someone else releases an enhanced version of the
3441 <tt>bar</tt> package (for example, a non-US variant), they
3443 <example compact="compact">
3447 and the <tt>bar-plus</tt> package will now also satisfy the
3448 dependency for the <tt>foo</tt> package.
3452 If a dependency or a conflict has a version number attached
3453 then only real packages will be considered to see whether
3454 the relationship is satisfied (or the prohibition violated,
3455 for a conflict) - it is assumed that a real package which
3456 provides the virtual package is not of the `right' version.
3457 So, a <tt>Provides</tt> field may not contain version
3458 numbers, and the version number of the concrete package
3459 which provides a particular virtual package will not be
3460 looked at when considering a dependency on or conflict with
3461 the virtual package name.
3465 It is likely that the ability will be added in a future
3466 release of <prgn>dpkg</prgn> to specify a version number for
3467 each virtual package it provides. This feature is not yet
3468 present, however, and is expected to be used only
3473 If you want to specify which of a set of real packages
3474 should be the default to satisfy a particular dependency on
3475 a virtual package, you should list the real package as an
3476 alternative before the virtual one.
3481 <sect id="replaces"><heading>Overwriting files and replacing
3482 packages - <tt>Replaces</tt></heading>
3485 The <tt>Replaces</tt> control file field has two distinct
3486 purposes, which come into play in different situations.
3489 <sect1><heading>Overwriting files in other packages</heading>
3492 Firstly, as mentioned before, it is usually an error for a
3493 package to contain files which are on the system in
3498 However, if the overwriting package declares that it
3499 <tt>Replaces</tt> the one containing the file being
3500 overwritten, then <prgn>dpkg</prgn> will replace the file
3501 from the old package with that from the new. The file
3502 will no longer be listed as `owned' by the old package.
3506 If a package is completely replaced in this way, so that
3507 <prgn>dpkg</prgn> does not know of any files it still
3508 contains, it is considered to have `disappeared'. It will
3509 be marked as not wanted on the system (selected for
3510 removal) and not installed. Any <tt>conffile</tt>s
3511 details noted for the package will be ignored, as they
3512 will have been taken over by the overwriting package. The
3513 package's <prgn>postrm</prgn> script will be run with a
3514 special argument to allow the package to do any final
3515 cleanup required. See <ref id="mscriptsinstact">.
3519 If an installed package, <tt>foo</tt> say, declares that
3520 it replaces another, <tt>bar</tt>, and an attempt is made
3521 to install <tt>bar</tt>, <prgn>dpkg</prgn> will discard
3522 files in the <tt>bar</tt> package which would overwrite
3523 those already present in <tt>foo</tt>. This is so that
3524 you can install an older version of a package without
3529 For this usage of <tt>Replaces</tt>, virtual packages (see
3530 <ref id="virtual">) are not considered when looking at a
3531 <tt>Replaces</tt> field - the packages declared as being
3532 replaced must be mentioned by their real names.
3536 Furthermore, this usage of <tt>Replaces</tt> only takes
3537 effect when both packages are at least partially on the
3538 system at once, so that it can only happen if they do not
3539 conflict or if the conflict has been overridden.
3544 <sect1><heading>Replacing whole packages, forcing their
3548 Secondly, <tt>Replaces</tt> allows the packaging system to
3549 resolve which package should be removed when there is a
3550 conflict - see <ref id="conflicts">. This usage only
3551 takes effect when the two packages <em>do</em> conflict,
3552 so that the two usages of this field do not interfere with
3557 In this situation, the package declared as being replaced
3558 can be a virtual package, so for example, all mail
3559 transport agents (MTAs) would have the following fields in
3560 their control files:
3561 <example compact="compact">
3562 Provides: mail-transport-agent
3563 Conflicts: mail-transport-agent
3564 Replaces: mail-transport-agent
3566 ensuring that only one MTA can be installed at any one
3571 <sect><heading>Relationships between source and binary packages -
3572 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3573 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
3577 A source package may declare a dependency or a conflict on a
3578 binary package, indicating which packages are required to be
3579 present on the system in order to build the binary packages
3580 from the source package. This is done with the control file
3581 fields <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3582 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>.
3583 The dependencies and conflicts they define must be satisfied
3584 (as defined earlier for binary packages) in order to invoke
3585 the targets in <tt>debian/rules</tt>, as follows:<footnote>
3587 If you make "build-arch" or "binary-arch", you need
3588 Build-Depends. If you make "build-indep" or
3589 "binary-indep", you need Build-Depends and
3590 Build-Depends-Indep. If you make "build" or "binary",
3594 There is no Build-Depends-Arch; the autobuilders will
3595 only need the Build-Depends if they know how to build
3596 only build-arch and binary-arch. Anyone building the
3597 build-indep/binary-indep targets is basically assumed to
3598 be building the whole package and so installs all build
3602 The purpose of the original split, I recall, was so that
3603 the autobuilders wouldn't need to install extra packages
3604 needed only for the binary-indep targets. But without a
3605 build-arch/build-indep split, this didn't work, since
3606 most of the work is done in the build target, not in the
3612 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
3615 The <tt>Build-Depends</tt> and
3616 <tt>Build-Conflicts</tt> fields must be satisfied when
3617 any of the following targets is invoked:
3618 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
3619 <tt>binary-arch</tt>, <tt>build-arch</tt>,
3620 <tt>build-indep</tt> and <tt>binary-indep</tt>.
3623 <tag><tt>Build-Depends-Indep</tt>,
3624 <tt>Build-Conflicts-Indep</tt></tag>
3627 The <tt>Build-Depends-Indep</tt> and
3628 <tt>Build-Conflicts-Indep</tt> fields must be
3629 satisfied when any of the following targets is
3630 invoked: <tt>build</tt>, <tt>clean</tt>,
3631 <tt>build-indep</tt>, <tt>binary</tt> and
3632 <tt>binary-indep</tt>.
3643 <chapt id="conffiles"><heading>Configuration file handling
3647 This chapter has been superseded by <ref id="config-files">.
3651 <chapt id="sharedlibs"><heading>Shared libraries</heading>
3654 Packages containing shared libraries must be constructed with
3655 a little care to make sure that the shared library is always
3656 available. This is especially important for packages whose
3657 shared libraries are vitally important, such as the C library
3658 (currently <tt>libc6</tt>).
3662 Firstly, the package should install the shared libraries under
3663 their normal names. For example, the <tt>libgdbmg1</tt>
3664 package should install <tt>libgdbm.so.1.7.3</tt> as
3665 <file>/usr/lib/libgdbm.so.1.7.3</file>. The files should not be
3666 renamed or re-linked by any <prgn>prerm</prgn> or
3667 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
3668 of renaming things safely without affecting running programs,
3669 and attempts to interfere with this are likely to lead to
3674 Secondly, the package should include the symbolic link that
3675 <prgn>ldconfig</prgn> would create for the shared libraries.
3676 For example, the <prgn>libgdbmg1</prgn> package should include
3677 a symbolic link from <file>/usr/lib/libgdbm.so.1</file> to
3678 <file>libgdbm.so.1.7.3</file>. This is needed so that the dynamic
3679 linker (for example <prgn>ld.so</prgn> or
3680 <prgn>ld-linux.so.*</prgn>) can find the library between the
3681 time that <prgn>dpkg</prgn> installs it and the time that
3682 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
3685 The package management system requires the library to be
3686 placed before the symbolic link pointing to it in the
3687 <file>.deb</file> file. This is so that when
3688 <prgn>dpkg</prgn> comes to install the symlink
3689 (overwriting the previous symlink pointing at an older
3690 version of the library), the new shared library is already
3691 in place. In the past, this was achieved by creating the
3692 library in the temporary packaging directory before
3693 creating the symlink. Unfortunately, this was not always
3694 effective, since the building of the tar file in the
3695 <file>.deb</file> depended on the behavior of the underlying
3696 file system. Some file systems (such as reiserfs) reorder
3697 the files so that the order of creation is forgotten.
3698 Starting with release <tt>1.7.0</tt>, <prgn>dpkg</prgn>
3699 will reorder the files itself as necessary when building a
3700 package. Thus it is no longer important to concern
3701 oneself with the order of file creation.
3707 Thirdly, the associated development package should contain a
3708 symlink for the shared library without a version number. For
3709 example, the <tt>libgdbmg1-dev</tt> package should include a
3710 symlink from <tt>/usr/lib/libgdbm.so</tt> to
3711 <file>libgdbm.so.1.7.3</file>. This symlink is needed by the
3712 linker (<prgn>ld</prgn>) when compiling packages, as it will
3713 only look for <file>libgdbm.so</file> when compiling dynamically.
3717 Any package installing shared libraries in one of the default
3718 library directories of the dynamic linker (which are currently
3719 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
3720 listed in <file>/etc/ld.so.conf</file><footnote>
3723 <list compact="compact">
3724 <item><p>/usr/X11R6/lib/Xaw3d</p></item>
3725 <item><p>/usr/local/lib</p></item>
3726 <item><p>/usr/lib/libc5-compat</p></item>
3727 <item><p>/lib/libc5-compat</p></item>
3728 <item><p>/usr/X11R6/lib</p></item>
3732 must use <prgn>ldconfig</prgn> to update the shared library
3733 system. The package must call <prgn>ldconfig</prgn> in the
3734 <prgn>postinst</prgn> script if the first argument is
3735 <tt>configure</tt>; the <prgn>postinst</prgn> script may
3736 optionally invoke <prgn>ldconfig</prgn> at other times. The
3737 package should call <prgn>ldconfig</prgn> in the
3738 <prgn>postrm</prgn> script if the first argument is
3739 <tt>remove</tt>. The maintainer scripts must not invoke
3740 <prgn>ldconfig</prgn> under any circumstances other than those
3741 described in this paragraph.<footnote>
3742 <p>During install or upgrade, the preinst is called before
3743 the new files are installed, so calling "ldconfig" is
3744 pointless. The preinst of an existing package can also be
3745 called if an upgrade fails. However, this happens during
3746 the critical time when a shared libs may exist on-disk
3747 under a temporary name. Thus, it is dangerous and
3748 forbidden by current policy to call "ldconfig" at this
3751 <p>When a package is installed or upgraded, "postinst
3752 configure" runs after the new files are safely on-disk.
3753 Since it is perfectly safe to invoke ldconfig
3754 unconditionally in a postinst, it is OK for a package to
3755 simply put ldconfig in its postinst without checking the
3756 argument. The postinst can also be called to recover from
3757 a failed upgrade. This happens before any new files are
3758 unpacked, so there is no reason to call "ldconfig" at this
3761 <p>For a package that is being removed, prerm is
3762 called with all the files intact, so calling ldconfig is
3763 useless. The other calls to "prerm" happen in the case of
3764 upgrade at a time when all the files of the old package
3765 are on-disk, so again calling "ldconfig" is pointless.
3767 <p>postrm, on the other hand, is called with the "remove"
3768 argument just after the files are removed, so this is the
3769 proper time to call "ldconfig" to notify the system of the
3770 fact shared libraries from the package are removed.
3771 The postrm can be called at several other times. At the
3772 time of "postrm purge", "postrm abort-install", or "postrm
3773 abort-upgrade", calling "ldconfig" is useless because the
3774 shared lib files are not on-disk. However, when "postrm"
3775 is invoked with arguments "upgrade", "failed-upgrade", or
3776 "disappear", a shared lib may exist on-disk under a
3783 <heading>Handling shared library dependencies - the
3784 <tt>shlibs</tt> system</heading>
3787 If a package contains a binary or library which links to a
3788 shared library, we must ensure that when the package is
3789 installed on the system, all of the libraries needed are
3790 also installed. This requirement led to the creation of the
3791 <tt>shlibs</tt> system, which is very simple in its design:
3792 any package which <em>provides</em> a shared library also
3793 provides information on the package dependencies required to
3794 ensure the presence of this library, and any package which
3795 <em>uses</em> a shared library uses this information to
3796 determine the dependencies it requires. The files which
3797 contain the mapping from shared libraries to the necessary
3798 dependency information are called <file>shlibs</file> files.
3802 Thus, when a package is built which contains any shared
3803 libraries, it must provide a <file>shlibs</file> file for other
3804 packages to use, and when a package is built which contains
3805 any shared libraries or compiled binaries, it must run
3806 <prgn>dpkg-shlibdeps</prgn> on these to determine the
3807 libraries used and hence the dependencies needed by this
3810 In the past, the shared libraries linked to were
3811 determined by calling <prgn>ldd</prgn>, but now
3812 <prgn>objdump</prgn> is used to do this. The only
3813 change this makes to package building is that
3814 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
3815 libraries, whereas in the past this was unnecessary.
3816 The rest of this footnote explains the advantage that
3821 We say that a binary <tt>foo</tt> <em>directly</em> uses
3822 a library <tt>libbar</tt> if it is explicitly linked
3823 with that library (that is, it uses the flag
3824 <tt>-lbar</tt> during the linking stage). Other
3825 libraries that are needed by <tt>libbar</tt> are linked
3826 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
3827 linker will load them automatically when it loads
3828 <tt>libbar</tt>. A package should depend on
3829 the libraries it directly uses, and the dependencies for
3830 those libraries should automatically pull in the other
3835 Unfortunately, the <prgn>ldd</prgn> program shows both
3836 the directly and indirectly used libraries, meaning that
3837 the dependencies determined included both direct and
3838 indirect dependencies. The use of <prgn>objdump</prgn>
3839 avoids this problem by determining only the directly
3844 A good example of where this helps is the following. We
3845 could update <tt>libimlib</tt> with a new version that
3846 supports a new graphics format called dgf (but retaining
3847 the same major version number). If we used the old
3848 <prgn>ldd</prgn> method, every package that uses
3849 <tt>libimlib</tt> would need to be recompiled so it
3850 would also depend on <tt>libdgf</tt> or it wouldn't run
3851 due to missing symbols. However with the new system,
3852 packages using <tt>libimlib</tt> can rely on
3853 <tt>libimlib</tt> itself having the dependency on
3854 <tt>libdgf</tt> and so they would not need rebuilding.
3860 In the following sections, we will first describe where the
3861 various <tt>shlibs</tt> files are to be found, then how to
3862 use <prgn>dpkg-shlibdeps</prgn>, and finally the
3863 <tt>shlibs</tt> file format and how to create them if your
3864 package contains a shared library.
3868 <sect><heading>The <tt>shlibs</tt> files present on the system
3872 There are several places where <tt>shlibs</tt> files are
3873 found. The following list gives them in the order in which
3874 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
3875 one which gives the required information is used.)
3881 <p><file>debian/shlibs.local</file></p>
3883 This lists overrides for this package. Its use is
3884 described below (see <ref id="shlibslocal">).
3889 <p><file>/etc/dpkg/shlibs.override</file></p>
3891 This lists global overrides. This list is normally
3892 empty. It is maintained by the local system
3898 <p><file>DEBIAN/shlibs</file> files in the `build directory'</p>
3900 When packages are being built, any
3901 <file>debian/shlibs</file> files are copied into the
3902 control file area of the temporary build directory and
3903 given the name <file>shlibs</file>. These files give
3904 details of any shared libraries included in the
3907 An example may help here. Let us say that the
3908 source package <tt>foo</tt> generates two binary
3909 packages, <tt>libfoo2</tt> and
3910 <tt>foo-runtime</tt>. When building the binary
3911 packages, the two packages are created in the
3912 directories <file>debian/libfoo2</file> and
3913 <file>debian/foo-runtime</file> respectively.
3914 (<file>debian/tmp</file> could be used instead of one
3915 of these.) Since <tt>libfoo2</tt> provides the
3916 <tt>libfoo</tt> shared library, it will require a
3917 <tt>shlibs</tt> file, which will be installed in
3918 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
3920 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
3921 when <prgn>dpkg-shlibdeps</prgn> is run on the
3923 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
3925 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
3926 determine whether <tt>foo-prog</tt>'s library
3927 dependencies are satisfied by any of the libraries
3928 provided by <tt>libfoo2</tt>. For this reason,
3929 <prgn>dpkg-shlibdeps</prgn> must only be run once
3930 all of the individual binary packages'
3931 <tt>shlibs</tt> files have been installed into the
3939 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
3941 These are the <file>shlibs</file> files corresponding to
3942 all of the packages installed on the system, and are
3943 maintained by the relevant package maintainers.
3948 <p><file>/etc/dpkg/shlibs.default</file></p>
3950 This file lists any shared libraries whose packages
3951 have failed to provide correct <file>shlibs</file> files.
3952 It was used when the <file>shlibs</file> setup was first
3953 introduced, but it is now normally empty. It is
3954 maintained by the <tt>dpkg</tt> maintainer.
3962 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
3963 <file>shlibs</file> files</heading>
3966 Put a call to <prgn>dpkg-shlibdeps</prgn> into your
3967 <file>debian/rules</file> file. If your package contains only
3968 compiled binaries and libraries (but no scripts), you can
3969 use a command such as:
3970 <example compact="compact">
3971 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
3972 debian/tmp/usr/lib/*
3974 Otherwise, you will need to explicitly list the compiled
3975 binaries and libraries.<footnote>
3977 If you are using <tt>debhelper</tt>, the
3978 <prgn>dh_shlibdeps</prgn> program will do this work for
3979 you. It will also correctly handle multi-binary
3986 This command puts the dependency information into the
3987 <file>debian/substvars</file> file, which is then used by
3988 <prgn>dpkg-gencontrol</prgn>. You will need to place a
3989 <tt>${shlib:Depends}</tt> variable in the <tt>Depends</tt>
3990 field in the control file for this to work.
3994 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
3995 done. If it does complain you might need to create your own
3996 <file>debian/shlibs.local</file> file, as explained below (see
3997 <ref id="shlibslocal">).
4001 If you have multiple binary packages, you will need to call
4002 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4003 compiled libraries or binaries. In such a case, you will
4004 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4005 utilities to specify a different <file>substvars</file> file.
4006 For more details on this and other options, see <manref
4007 name="dpkg-shlibdeps" section="1">.
4011 <sect id="shlibs"><heading>The <file>shlibs</file> File Format
4015 Each <file>shlibs</file> file has the same format. Lines
4016 beginning with <tt>#</tt> are considered to be comments and
4017 are ignored. Each line is of the form:
4018 <example compact="compact">
4019 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4024 We will explain this by reference to the example of the
4025 <tt>zlib1g</tt> package, which (at the time of writing)
4026 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4030 <var>library-name</var> is the name of the shared library,
4031 in this case <tt>libz</tt>. (This must match the name part
4032 of the soname, see below.)
4036 <var>soname-version-number</var> is the version part of the
4037 soname of the library. The soname is the thing that must
4038 exactly match for the library to be recognized by the
4039 dynamic linker, and is usually of the form
4040 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4041 example, <tt>libz.so.1</tt>.<footnote>
4043 This can be determined using the command
4044 <example compact="compact">
4045 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
4049 The version part is the part which comes after
4050 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
4054 <var>dependencies</var> has the same syntax as a dependency
4055 field in a binary package control file. It should give
4056 details of which packages are required to satisfy a binary
4057 built against the version of the library contained in the
4058 package. See <ref id="depsyntax"> for details.
4062 In our example, if the first version of the <tt>zlib1g</tt>
4063 package which contained a minor number of at least
4064 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
4065 <tt>shlibs</tt> entry for this library could say:
4066 <example compact="compact">
4067 libz 1 zlib1g (>= 1:1.1.3)
4069 The version-specific dependency is to avoid warnings from
4070 the dynamic linker about using older shared libraries with
4076 <heading>Providing a <file>shlibs</file> file</heading>
4079 If your package provides a shared library, you should create
4080 a <file>shlibs</file> file following the format described above.
4081 It is usual to call this file <file>debian/shlibs</file> (but if
4082 you have multiple binary packages, you might want to call it
4083 <file>debian/shlibs.<var>package</var></file> instead). Then
4084 let <file>debian/rules</file> install it in the control area:
4085 <example compact="compact">
4086 install -m644 debian/shlibs debian/tmp/DEBIAN
4088 or, in the case of a multi-binary package:
4089 <example compact="compact">
4090 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
4092 An alternative way of doing this is to create the
4093 <file>shlibs</file> file in the control area directly from
4094 <file>debian/rules</file> without using a <file>debian/shlibs</file>
4095 file at all,<footnote>
4097 This is what <prgn>dh_makeshlibs</prgn> in the
4098 <tt>debhelper</tt> suite does.
4101 since the <file>debian/shlibs</file> file itself is ignored by
4102 <prgn>dpkg-shlibdeps</prgn>.
4106 As <prgn>dpkg-shlibdeps</prgn> reads the
4107 <file>DEBIAN/shlibs</file> files in all of the binary packages
4108 being built from this source package, all of the
4109 <file>DEBIAN/shlibs</file> files should be installed before
4110 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
4115 <sect id="shlibslocal">
4116 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
4119 This file is intended only as a <em>temporary</em> fix if
4120 your binaries or libraries depend on a library whose package
4121 does not yet provide a correct <file>shlibs</file> file.
4125 We will assume that you are trying to package a binary
4126 <tt>foo</tt>. When you try running
4127 <prgn>dpkg-shlibdeps</prgn> you get the following error
4128 message (<tt>-O</tt> displays the dependency information on
4129 <tt>stdout</tt> instead of writing it to
4130 <tt>debian/substvars</tt>, and the lines have been wrapped
4131 for ease of reading):
4132 <example compact="compact">
4133 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
4134 dpkg-shlibdeps: warning: unable to find dependency
4135 information for shared library libbar (soname 1,
4136 path /usr/lib/libbar.so.1, dependency field Depends)
4137 shlibs:Depends=libc6 (>= 2.2.2-2)
4139 You can then run <prgn>ldd</prgn> on the binary to find the
4140 full location of the library concerned:
4141 <example compact="compact">
4143 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
4144 libc.so.6 => /lib/libc.so.6 (0x40032000)
4145 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
4147 So the <prgn>foo</prgn> binary depends on the
4148 <prgn>libbar</prgn> shared library, but no package seems to
4149 provide a <file>*.shlibs</file> file handling
4150 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
4151 determine the package responsible:
4152 <example compact="compact">
4153 $ dpkg -S /usr/lib/libbar.so.1
4154 bar1: /usr/lib/libbar.so.1
4155 $ dpkg -s bar1 | grep Version
4158 This tells us that the <tt>bar1</tt> package, version 1.0-1,
4159 is the one we are using. Now we can file a bug against the
4160 <tt>bar1</tt> package and create our own
4161 <file>debian/shlibs.local</file> to locally fix the problem.
4162 Including the following line into your
4163 <file>debian/shlibs.local</file> file:
4164 <example compact="compact">
4165 libbar 1 bar1 (>= 1.0-1)
4167 should allow the package build to work.
4171 As soon as the maintainer of <tt>bar1</tt> provides a
4172 correct <file>shlibs</file> file, you should remove this line
4173 from your <file>debian/shlibs.local</file> file. (You should
4174 probably also then have a versioned <tt>Build-Depends</tt>
4175 on <tt>bar1</tt> to help ensure that others do not have the
4176 same problem building your package.)
4181 <chapt id="opersys"><heading>The Operating System</heading>
4184 <heading>Filesystem hierarchy</heading>
4188 <heading>Filesystem Structure</heading>
4191 The location of all installed files and directories must
4192 comply with the Filesystem Hierarchy Standard (FHS),
4193 version 2.1, except where doing so would violate other
4194 terms of Debian Policy. The version of this document
4195 referred here can be found in the <tt>debian-policy</tt>
4197 <url id="http://www.debian.org/doc/packaging-manuals/fhs/"
4198 name="FHS (Debian copy)"> alongside this manual (or, if
4199 you have the <package>debian-policy</package> installed,
4201 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
4202 (local copy)">). The
4203 latest version, which may be a more recent version, may
4205 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
4206 Specific questions about following the standard may be
4207 asked on the <tt>debian-devel</tt> mailing list, or
4208 referred to the FHS mailing list (see the
4209 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
4215 <heading>Site-specific programs</heading>
4218 As mandated by the FHS, packages must not place any
4219 files in <file>/usr/local</file>, either by putting them in
4220 the file system archive to be unpacked by <prgn>dpkg</prgn>
4221 or by manipulating them in their maintainer scripts.
4225 However, the package may create empty directories below
4226 <file>/usr/local</file> so that the system administrator knows
4227 where to place site-specific files. These directories
4228 should be removed on package removal if they are
4233 Note, that this applies only to directories <em>below</em>
4234 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
4235 Packages must not create sub-directories in the directory
4236 <file>/usr/local</file> itself, except those listed in FHS,
4237 section 4.5. However, you may create directories below
4238 them as you wish. You must not remove any of the
4239 directories listed in 4.5, even if you created them.
4243 Since <file>/usr/local</file> can be mounted read-only from a
4244 remote server, these directories must be created and
4245 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
4246 maintainer scripts and not be included in the
4247 <file>.deb</file> archive. These scripts must not fail if
4248 either of these operations fail.
4252 For example, the <tt>emacsen-common</tt> package could
4253 contain something like
4254 <example compact="compact">
4255 if [ ! -e /usr/local/share/emacs ]
4257 if mkdir /usr/local/share/emacs 2>/dev/null
4259 chown root:staff /usr/local/share/emacs
4260 chmod 2775 /usr/local/share/emacs
4264 in its <prgn>postinst</prgn> script, and
4265 <example compact="compact">
4266 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
4267 rmdir /usr/local/share/emacs 2>/dev/null || true
4269 in the <prgn>prerm</prgn> script. (Note that this form is
4270 used to ensure that if the script is interrupted, the
4271 directory <file>/usr/local/share/emacs</file> will still be
4276 If you do create a directory in <file>/usr/local</file> for
4277 local additions to a package, you should ensure that
4278 settings in <file>/usr/local</file> take precedence over the
4279 equivalents in <file>/usr</file>.
4283 However, because <file>/usr/local</file> and its contents are
4284 for exclusive use of the local administrator, a package
4285 must not rely on the presence or absence of files or
4286 directories in <file>/usr/local</file> for normal operation.
4290 The <file>/usr/local</file> directory itself and all the
4291 subdirectories created by the package should (by default) have
4292 permissions 2775 (group-writable and set-group-id) and be
4293 owned by <tt>root.staff</tt>.
4298 <heading>The system-wide mail directory</heading>
4300 The system-wide mail directory is <file>/var/mail</file>. This
4301 directory is part of the base system and should not owned
4302 by any particular mail agents. The use of the old
4303 location <file>/var/spool/mail</file> is deprecated, even
4304 though the spool may still be physically located there.
4305 To maintain partial upgrade compatibility for systems
4306 which have <file>/var/spool/mail</file> as their physical mail
4307 spool, packages using <file>/var/mail</file> must depend on
4308 either <package>libc6</package> (>= 2.1.3-13), or on
4309 <package>base-files</package> (>= 2.2.0), or on later
4310 versions of either one of these packages.
4316 <heading>Users and groups</heading>
4319 <heading>Introduction</heading>
4321 The Debian system can be configured to use either plain or
4326 Some user ids (UIDs) and group ids (GIDs) are reserved
4327 globally for use by certain packages. Because some
4328 packages need to include files which are owned by these
4329 users or groups, or need the ids compiled into binaries,
4330 these ids must be used on any Debian system only for the
4331 purpose for which they are allocated. This is a serious
4332 restriction, and we should avoid getting in the way of
4333 local administration policies. In particular, many sites
4334 allocate users and/or local system groups starting at 100.
4338 Apart from this we should have dynamically allocated ids,
4339 which should by default be arranged in some sensible
4340 order, but the behavior should be configurable.
4344 Packages other than <tt>base-passwd</tt> must not modify
4345 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
4346 <file>/etc/group</file> or <file>/etc/gshadow</file>.
4351 <heading>UID and GID classes</heading>
4353 The UID and GID numbers are divided into classes as
4359 Globally allocated by the Debian project, the same
4360 on every Debian system. These ids will appear in
4361 the <file>passwd</file> and <file>group</file> files of all
4362 Debian systems, new ids in this range being added
4363 automatically as the <tt>base-passwd</tt> package is
4368 Packages which need a single statically allocated
4369 uid or gid should use one of these; their
4370 maintainers should ask the <tt>base-passwd</tt>
4378 Dynamically allocated system users and groups.
4379 Packages which need a user or group, but can have
4380 this user or group allocated dynamically and
4381 differently on each system, should use <tt>adduser
4382 --system</tt> to create the group and/or user.
4383 <prgn>adduser</prgn> will check for the existence of
4384 the user or group, and if necessary choose an unused
4385 id based on the ranges specified in
4386 <file>adduser.conf</file>.
4390 <tag>1000-29999:</tag>
4393 Dynamically allocated user accounts. By default
4394 <prgn>adduser</prgn> will choose UIDs and GIDs for
4395 user accounts in this range, though
4396 <file>adduser.conf</file> may be used to modify this
4401 <tag>30000-59999:</tag>
4406 <tag>60000-64999:</tag>
4409 Globally allocated by the Debian project, but only
4410 created on demand. The ids are allocated centrally
4411 and statically, but the actual accounts are only
4412 created on users' systems on demand.
4416 These ids are for packages which are obscure or
4417 which require many statically-allocated ids. These
4418 packages should check for and create the accounts in
4419 <file>/etc/passwd</file> or <file>/etc/group</file> (using
4420 <prgn>adduser</prgn> if it has this facility) if
4421 necessary. Packages which are likely to require
4422 further allocations should have a `hole' left after
4423 them in the allocation, to give them room to
4428 <tag>65000-65533:</tag>
4436 User <tt>nobody</tt>. The corresponding gid refers
4437 to the group <tt>nogroup</tt>.
4444 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
4445 not</em> be used, because it is the error return
4454 <sect id="sysvinit">
4455 <heading>System run levels and <file>init.d</file> scripts</heading>
4457 <sect1 id="/etc/init.d">
4458 <heading>Introduction</heading>
4461 The <file>/etc/init.d</file> directory contains the scripts
4462 executed by <prgn>init</prgn> at boot time and when the
4463 init state (or `runlevel') is changed (see <manref
4464 name="init" section="8">).
4468 There are at least two different, yet functionally
4469 equivalent, ways of handling these scripts. For the sake
4470 of simplicity, this document describes only the symbolic
4471 link method. However, it must not be assumed by maintainer
4472 scripts that this method is being used, and any automated
4473 manipulation of the various runlevel behaviours by
4474 maintainer scripts must be performed using
4475 <prgn>update-rc.d</prgn> as described below and not by
4476 manually installing or removing symlinks. For information
4477 on the implementation details of the other method,
4478 implemented in the <tt>file-rc</tt> package, please refer
4479 to the documentation of that package.
4483 These scripts are referenced by symbolic links in the
4484 <file>/etc/rc<var>n</var>.d</file> directories. When changing
4485 runlevels, <prgn>init</prgn> looks in the directory
4486 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
4487 execute, where <tt><var>n</var></tt> is the runlevel that
4488 is being changed to, or <tt>S</tt> for the boot-up
4493 The names of the links all have the form
4494 <file>S<var>mm</var><var>script</var></file> or
4495 <file>K<var>mm</var><var>script</var></file> where
4496 <var>mm</var> is a two-digit number and <var>script</var>
4497 is the name of the script (this should be the same as the
4498 name of the actual script in <file>/etc/init.d</file>).
4502 When <prgn>init</prgn> changes runlevel first the targets
4503 of the links whose names start with a <tt>K</tt> are
4504 executed, each with the single argument <tt>stop</tt>,
4505 followed by the scripts prefixed with an <tt>S</tt>, each
4506 with the single argument <tt>start</tt>. (The links are
4507 those in the <file>/etc/rc<var>n</var>.d</file> directory
4508 corresponding to the new runlevel.) The <tt>K</tt> links
4509 are responsible for killing services and the <tt>S</tt>
4510 link for starting services upon entering the runlevel.
4514 For example, if we are changing from runlevel 2 to
4515 runlevel 3, init will first execute all of the <tt>K</tt>
4516 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
4517 all of the <tt>S</tt> prefixed scripts in that directory.
4518 The links starting with <tt>K</tt> will cause the
4519 referred-to file to be executed with an argument of
4520 <tt>stop</tt>, and the <tt>S</tt> links with an argument
4525 The two-digit number <var>mm</var> is used to determine
4526 the order in which to run the scripts: low-numbered links
4527 have their scripts run first. For example, the
4528 <tt>K20</tt> scripts will be executed before the
4529 <tt>K30</tt> scripts. This is used when a certain service
4530 must be started before another. For example, the name
4531 server <prgn>bind</prgn> might need to be started before
4532 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
4533 can set up its access lists. In this case, the script
4534 that starts <prgn>bind</prgn> would have a lower number
4535 than the script that starts <prgn>inn</prgn> so that it
4537 <example compact="compact">
4544 The two runlevels 0 (halt) and 6 (reboot) are slightly
4545 different. In these runlevels, the links with an
4546 <tt>S</tt> prefix are still called after those with a
4547 <tt>K</tt> prefix, but they too are called with the single
4548 argument <tt>stop</tt>.
4552 Also, if the script name ends <tt>.sh</tt>, the script
4553 will be sourced in runlevel <tt>S</tt> rather that being
4554 run in a forked subprocess, but will be explicitly run by
4555 <prgn>sh</prgn> in all other runlevels.
4560 <heading>Writing the scripts</heading>
4563 Packages that include daemons for system services should
4564 place scripts in <file>/etc/init.d</file> to start or stop
4565 services at boot time or during a change of runlevel.
4566 These scripts should be named
4567 <file>/etc/init.d/<var>package</var></file>, and they should
4568 accept one argument, saying what to do:
4571 <tag><tt>start</tt></tag>
4572 <item><p>start the service,</p></item>
4574 <tag><tt>stop</tt></tag>
4575 <item><p>stop the service,</p></item>
4577 <tag><tt>restart</tt></tag>
4578 <item><p>stop and restart the service,</p></item>
4580 <tag><tt>reload</tt></tag>
4581 <item><p>cause the configuration of the service to be
4582 reloaded without actually stopping and restarting
4583 the service,</p></item>
4585 <tag><tt>force-reload</tt></tag>
4586 <item><p>cause the configuration to be reloaded if the
4587 service supports this, otherwise restart the
4591 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
4592 <tt>force-reload</tt> options should be supported by all
4593 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
4594 option is optional.</p>
4597 The <file>init.d</file> scripts should ensure that they will
4598 behave sensibly if invoked with <tt>start</tt> when the
4599 service is already running, or with <tt>stop</tt> when it
4600 isn't, and that they don't kill unfortunately-named user
4601 processes. The best way to achieve this is usually to use
4602 <prgn>start-stop-daemon</prgn>.</p>
4605 If a service reloads its configuration automatically (as
4606 in the case of <prgn>cron</prgn>, for example), the
4607 <tt>reload</tt> option of the <file>init.d</file> script
4608 should behave as if the configuration has been reloaded
4612 The <file>/etc/init.d</file> scripts must be treated as
4613 configuration files, either (if they are present in the
4614 package, that is, in the .deb file) by marking them as
4615 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
4616 by managing them correctly in the maintainer scripts (see
4617 <ref id="config-files">). This is important since we want
4618 to give the local system administrator the chance to adapt
4619 the scripts to the local system, e.g., to disable a
4620 service without de-installing the package, or to specify
4621 some special command line options when starting a service,
4622 while making sure her changes aren't lost during the next
4627 These scripts should not fail obscurely when the
4628 configuration files remain but the package has been
4629 removed, as configuration files remain on the system after
4630 the package has been removed. Only when <prgn>dpkg</prgn>
4631 is executed with the <tt>--purge</tt> option will
4632 configuration files be removed. In particular, as the
4633 <file>/etc/init.d/<var>package</var></file> script itself is
4634 usually a <tt>conffile</tt>, it will remain on the system
4635 if the package is removed but not purged. Therefore, you
4636 should include a <tt>test</tt> statement at the top of the
4638 <example compact="compact">
4639 test -f <var>program-executed-later-in-script</var> || exit 0
4644 Often there are some variables in the <file>init.d</file>
4645 scripts whose values control the behaviour of the scripts,
4646 and which a system administrator is likely to want to
4647 change. As the scripts themselves are frequently
4648 <tt>conffile</tt>s, modifying them requires that the
4649 administrator merge in their changes each time the package
4650 is upgraded and the <tt>conffile</tt> changes. To ease
4651 the burden on the system administrator, such configurable
4652 values should not be placed directly in the script.
4653 Instead, they should be placed in a file in
4654 <file>/etc/default</file>, which typically will have the same
4655 base name as the <file>init.d</file> script. This extra file
4656 should be sourced by the script when the script runs. It
4657 must contain only variable settings and comments in POSIX
4658 <prgn>sh</prgn> format. It may either be a
4659 <tt>conffile</tt> or a configuration file maintained by
4660 the package maintainer scripts. See <ref id="config-files">
4665 To ensure that vital configurable values are always
4666 available, the <file>init.d</file> script should set default
4667 values for each of the shell variables it uses, either
4668 before sourcing the <file>/etc/default/</file> file or
4669 afterwards using something like the <tt>:
4670 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
4671 script must behave sensibly and not fail if the
4672 <file>/etc/default</file> file is deleted.
4677 <heading>Interfacing with the initscript system</heading>
4680 Maintainers should use the abstraction layer provided by
4681 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
4682 programs to deal with initscripts in their packages'
4683 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
4684 and <prgn>postrm</prgn>.
4687 Directly managing the /etc/rc?.d links and directly
4688 invoking the <file>/etc/init.d/</file> initscripts should
4689 be done only by packages providing the initscript
4690 subsystem (such as <prgn>sysvinit</prgn> and
4691 <prgn>file-rc</prgn>).
4696 <heading>Managing the links</heading>
4699 The program <prgn>update-rc.d</prgn> is provided for
4700 package maintainers to arrange for the proper creation and
4701 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
4702 or their functional equivalent if another method is being
4703 used. This may be used by maintainers in their packages'
4704 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.</p>
4707 You must not include any <file>/etc/rc<var>n</var>.d</file>
4708 symbolic links in the actual archive or manually create or
4709 remove the symbolic links in maintainer scripts; you must
4710 use the <prgn>update-rc.d</prgn> program instead. (The
4711 former will fail if an alternative method of maintaining
4712 runlevel information is being used.) You must not include
4713 the <file>/etc/rc<var>n</var>.d</file> directories themselves
4714 in the archive either. (Only the <tt>sysvinit</tt>
4719 By default <prgn>update-rc.d</prgn> will start services in
4720 each of the multi-user state runlevels (2, 3, 4, and 5)
4721 and stop them in the halt runlevel (0), the single-user
4722 runlevel (1) and the reboot runlevel (6). The system
4723 administrator will have the opportunity to customize
4724 runlevels by simply adding, moving, or removing the
4725 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
4726 symbolic links are being used, or by modifying
4727 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
4732 To get the default behavior for your package, put in your
4733 <prgn>postinst</prgn> script
4734 <example compact="compact">
4735 update-rc.d <var>package</var> defaults
4737 and in your <prgn>postrm</prgn>
4738 <example compact="compact">
4739 if [ "$1" = purge ]; then
4740 update-rc.d <var>package</var> remove
4742 </example>. Note that is your package changes runlevels
4743 or priority, you may have to remove and recreate the
4744 links, since otherwise the old links may
4745 persist. Refer to the documentation of
4746 <prgn>update-rc.d</prgn></p>
4749 This will use a default sequence number of 20. If it does
4750 not matter when or in which order the <file>init.d</file>
4751 script is run, use this default. If it does, then you
4752 should talk to the maintainer of the <prgn>sysvinit</prgn>
4753 package or post to <tt>debian-devel</tt>, and they will
4754 help you choose a number.
4758 For more information about using <tt>update-rc.d</tt>,
4759 please consult its manpage <manref name="update-rc.d"
4765 <heading>Running initscripts</heading>
4767 The program <prgn>invoke-rc.d</prgn> is provided to make
4768 it easier for package maintainers to properly invoke an
4769 initscript, obeying runlevel and other locally-defined
4770 constraints that might limit a package's right to start,
4771 stop and otherwise manage services. This program may be
4772 used by maintainers in their packages' scripts.
4775 The use of <prgn>invoke-rc.d</prgn> to invoke the
4776 <file>/etc/init.d/*</file> initscripts is strongly
4777 recommended<footnote>
4779 In the future, the use of invoke-rc.d to invoke
4780 initscripts shall be made mandatory. Maintainers are
4781 advised to switch to invoke-rc.d as soon as
4783 </footnote>, instead of calling them directly.
4787 By default, <prgn>invoke-rc.d</prgn> will pass any
4788 action requests (start, stop, reload, restart...) to the
4789 <file>/etc/init.d</file> script, filtering out requests
4790 to start or restart a service out of its intended
4794 Most packages will simply need to change:
4795 <example compact="compact">/etc/init.d/<package>
4796 <action></example> in their <prgn>postinst</prgn>
4797 and <prgn>prerm</prgn> scripts to:
4798 <example compact="compact">
4799 if [ -x /usr/sbin/invoke-rc.d ] ; then
4800 invoke-rc.d <var>package</var> <action>
4802 /etc/init.d/<var>package</var> <action>
4806 A package should register its initscript services using
4807 <prgn>update-rc.d</prgn> before it tries to invoke them
4808 using <prgn>invoke-rc.d</prgn>. Invocation of
4809 unregistered services may fail.
4812 For more information about using
4813 <prgn>invoke-rc.d</prgn>, please consult its manpage
4814 <manref name="invoke-rc.d" section="8">.
4821 <heading>Boot-time initialization</heading>
4824 There used to be another directory, <file>/etc/rc.boot</file>,
4825 which contained scripts which were run once per machine
4826 boot. This has been deprecated in favour of links from
4827 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
4828 described in <ref id="/etc/init.d">. Packages must not
4829 place files in <file>/etc/rc.boot</file>.</p>
4832 <heading>Example</heading>
4835 The <prgn>bind</prgn> DNS (nameserver) package wants to
4836 make sure that the nameserver is running in multiuser
4837 runlevels, and is properly shut down with the system. It
4838 puts a script in <file>/etc/init.d</file>, naming the script
4839 appropriately <tt>bind</tt>. As you can see, the script
4840 interprets the argument <tt>reload</tt> to send the
4841 nameserver a <tt>HUP</tt> signal (causing it to reload its
4842 configuration); this way the system administrator can say
4843 <file>/etc/init.d/bind reload</file> to reload the name
4844 server. The script has one configurable value, which can
4845 be used to pass parameters to the named program at
4846 startup; this value is read from
4847 <file>/etc/default/bind</file> (see below).
4851 <example compact="compact">
4854 # Original version by Robert Leslie
4855 # <rob@mars.org>, edited by iwj and cs
4857 test -x /usr/sbin/named || exit 0
4859 # Source defaults file.
4861 if [ -f /etc/default/bind ]; then
4868 echo -n "Starting domain name service: named"
4869 start-stop-daemon --start --quiet --exec /usr/sbin/named \
4874 echo -n "Stopping domain name service: named"
4875 start-stop-daemon --stop --quiet \
4876 --pidfile /var/run/named.pid --exec /usr/sbin/named
4880 echo -n "Restarting domain name service: named"
4881 start-stop-daemon --stop --quiet \
4882 --pidfile /var/run/named.pid --exec /usr/sbin/named
4883 start-stop-daemon --start --verbose --exec /usr/sbin/named \
4887 force-reload|reload)
4888 echo -n "Reloading configuration of domain name service: named"
4889 start-stop-daemon --stop --signal 1 --quiet \
4890 --pidfile /var/run/named.pid --exec /usr/sbin/named
4894 echo "Usage: /etc/init.d/bind " \
4895 " {start|stop|restart|reload|force-reload}" >&2
4905 Complementing the above init script is a configuration
4906 file <file>/etc/default/bind</file>, which contains
4907 configurable parameters used by the script. This would be
4908 created by the <prgn>postinst</prgn> script if it was not
4909 already present, and removed on purge by the
4910 <prgn>postrm</prgn> script.
4911 <example compact="compact">
4912 # Specified parameters to pass to named. See named(8).
4913 # You may uncomment the following line, and edit to taste.
4919 Another example on which you can base your
4920 <file>/etc/init.d</file> scripts is found in
4921 <file>/etc/init.d/skeleton</file>.
4925 If this package is happy with the default setup from
4926 <prgn>update-rc.d</prgn>, namely an ordering number of 20
4927 and having named running in all runlevels, it can say in
4928 its <prgn>postinst</prgn>:
4929 <example compact="compact">
4930 update-rc.d bind defaults >/dev/null
4932 And in its <prgn>postrm</prgn>, to remove the links when the
4934 <example compact="compact">
4935 if [ "$1" = purge ]; then
4936 update-rc.d bind remove >/dev/null
4944 <heading>Console messages from <file>init.d</file> scripts</heading>
4947 This section describes the formats to be used for messages
4948 written to standard output by the <file>/etc/init.d</file>
4949 scripts. The intent is to improve the consistency of
4950 Debian's startup and shutdown look and feel. For this
4951 reason, please look very carefully at the details. We want
4952 the messages to have the same format in terms of wording,
4953 spaces, punctuation and case of letters.
4957 Here is a list of overall rules that you should use when you
4958 create output messages. They can be useful if you have a
4959 non-standard message that is not covered specifically in the
4967 Every message should fit in one line (fewer than 80
4968 characters), start with a capital letter and end with
4969 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
4975 If you want to express that the computer is working on
4976 something (that is, performing a specific task, not
4977 starting or stopping a program), we use an "ellipsis"
4978 (three dots: <tt>...</tt>). Note that we don't insert
4979 spaces before or after the dots. If the task has been
4980 completed we write <tt>done.</tt> and a line feed.
4986 Design your messages as if the computer is telling you
4987 what he is doing (let him be polite :-), but don't
4988 mention "him" directly. For example, if you think of
4990 <example compact="compact">
4991 I'm starting network daemons: nfsd mountd.
4994 <example compact="compact">
4995 Starting network daemons: nfsd mountd.
5003 There are standard message formats for the following
5004 situations. They should be used by the <tt>init.d</tt>
5011 <p>When daemons are started</p>
5014 If your script starts one or more daemons, the output
5015 should look like this (a single line, no leading
5017 <example compact="compact">
5018 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5020 The <var>description</var> should describe the
5021 subsystem the daemon or set of daemons are part of,
5022 while <var>daemon-1</var> up to <var>daemon-n</var>
5023 denote each daemon's name (typically the file name of
5028 For example, the output of <file>/etc/init.d/lpd</file>
5030 <example compact="compact">
5031 Starting printer spooler: lpd.
5036 This can be achieved by saying
5037 <example compact="compact">
5038 echo -n "Starting printer spooler: lpd"
5039 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5042 in the script. If you have more than one daemon to
5043 start, you should do the following:
5044 <example compact="compact">
5045 echo -n "Starting remote file system services:"
5046 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5047 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5048 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5051 This makes it possible for the user to see what takes
5052 so long and when the final daemon has been started.
5053 You should be careful where to put spaces: in the
5054 example above the system administrator can easily
5055 comment out a line if he don't wants to start a
5056 specific daemon, while the displayed message still
5062 <p>When a system parameter is being set</p>
5065 If you have to set up different system parameters
5066 during the system boot, you should use this format:
5067 <example compact="compact">
5068 Setting <var>parameter</var> to `<var>value</var>'.
5073 You can use a statement such as the following to get
5075 <example compact="compact">
5076 echo "Setting DNS domainname to \`$domainname'."
5081 Note that the left quotation mark (<tt>`</tt>) is
5082 different from the right one (<tt>'</tt>).
5087 <p>When a daemon is stopped or restarted</p>
5090 When you stop or restart a daemon, you should issue a
5091 message identical to the startup message, except that
5092 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
5093 or <tt>Restarting</tt> respectively.
5097 For example, stopping the printer daemon will like
5099 <example compact="compact">
5100 Stopping printer spooler: lpd.
5106 <p>When something is executed</p>
5109 There are several examples where you have to run a
5110 program at system startup or shutdown to perform a
5111 specific task, for example, setting the system's clock
5112 using <prgn>netdate</prgn> or killing all processes
5113 when the system shuts down. Your message should look
5115 <example compact="compact">
5116 Doing something very useful...done.
5118 You should print the <tt>done.</tt> immediately after
5119 the job has been completed, so that the user is
5120 informed why she has to wait. You can get this
5122 <example compact="compact">
5123 echo -n "Doing something very useful..."
5132 <p>When the configuration is reloaded</p>
5135 When a daemon is forced to reload its configuration
5136 files you should use the following format:
5137 <example compact="compact">
5138 Reloading <var>description</var> configuration...done.
5140 where <var>description</var> is the same as in the
5141 daemon starting message.
5149 <heading>Cron jobs</heading>
5152 Packages must not modify the configuration file
5153 <file>/etc/crontab</file>, and they must not modify the files in
5154 <file>/var/spool/cron/crontabs</file>.</p>
5157 If a package wants to install a job that has to be executed
5158 via cron, it should place a file with the name of the
5159 package in one or more of the following directories:
5160 <example compact="compact">
5165 As these directory names imply, the files within them are
5166 executed on a daily, weekly, or monthly basis,
5167 respectively. The exact times are listed in
5168 <file>/etc/crontab</file>.</p>
5171 All files installed in any of these directories must be
5172 scripts (e.g., shell scripts or Perl scripts) so that they
5173 can easily be modified by the local system administrator.
5174 In addition, they should be treated as configuration
5179 If a certain job has to be executed more frequently than
5180 daily, the package should install a file
5181 <file>/etc/cron.d/<var>package</var></file>. This file uses the
5182 same syntax as <file>/etc/crontab</file> and is processed by
5183 <prgn>cron</prgn> automatically. The file must also be
5184 treated as a configuration file. (Note that entries in the
5185 <file>/etc/cron.d</file> directory are not handled by
5186 <prgn>anacron</prgn>. Thus, you should only use this
5187 directory for jobs which may be skipped if the system is not
5191 The scripts or crontab entries in these directories should
5192 check if all necessary programs are installed before they
5193 try to execute them. Otherwise, problems will arise when a
5194 package was removed but not purged since configuration files
5195 are kept on the system in this situation.</p>
5199 <heading>Menus</heading>
5202 Menu entries should follow the current menu policy found in
5203 the <tt>menu-policy</tt> files in the <tt>debian-policy</tt>
5204 package. It may also be found on the Debian FTP site
5205 <ftpsite>ftp.debian.org</ftpsite> as the file
5206 <ftppath>/debian/doc/package-developer/menu-policy.txt.gz</ftppath>,
5207 or in the equivalent location on your local mirror.
5211 The Debian <tt>menu</tt> package provides a standard
5212 interface between packages providing applications and
5213 documents, and <em>menu programs</em> (either X window
5214 managers or text-based menu programs such as
5215 <prgn>pdmenu</prgn>).
5219 All packages that provide applications that need not be
5220 passed any special command line arguments for normal
5221 operation should register a menu entry for those
5222 applications, so that users of the <tt>menu</tt> package
5223 will automatically get menu entries in their window
5224 managers, as well in shells like <tt>pdmenu</tt>.</p>
5227 Please also refer to the <em>Debian Menu System</em>
5228 documentation that comes with the <tt>menu</tt> package for
5229 information about how to register your applications and web
5235 <heading>Multimedia handlers</heading>
5238 Packages which provide the ability to view/show/play,
5239 compose, edit or print MIME types should register themselves
5240 as such following the current MIME support policy found in
5241 the <tt>mime-policy</tt> files in the <tt>debian-policy</tt>
5242 package. It may also be found on the Debian FTP site
5243 <ftpsite>ftp.debian.org</ftpsite> as the file
5244 <ftppath>/debian/doc/package-developer/mime-policy.txt.gz</ftppath>,
5245 or in the equivalent location on your local mirror.
5249 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
5250 is a mechanism for encoding files and data streams and
5251 providing meta-information about them, in particular their
5252 type (e.g. audio or video) and format (e.g. PNG, HTML,
5257 Registration of MIME type handlers allows programs like mail
5258 user agents and web browsers to to invoke these handlers to
5259 view, edit or display MIME types they don't support
5265 <heading>Keyboard configuration</heading>
5268 To achieve a consistent keyboard configuration so that all
5269 applications interpret a keyboard event the same way, all
5270 programs in the Debian distribution must be configured to
5271 comply with the following guidelines.
5275 The following keys must have the specified interpretations:
5278 <tag><tt><--</tt></tag>
5279 <item><p>delete the character to the left of the cursor</p></item>
5281 <tag><tt>Delete</tt></tag>
5282 <item><p>delete the character to the right of the cursor</p></item>
5284 <tag><tt>Control+H</tt></tag>
5285 <item><p>emacs: the help prefix</p></item>
5288 The interpretation of any keyboard events should be
5289 independent of the terminal that is used, be it a virtual
5290 console, an X terminal emulator, an rlogin/telnet session,
5295 The following list explains how the different programs
5296 should be set up to achieve this:
5301 <item><p><tt><--</tt> generates <tt>KB_BackSpace</tt>
5304 <item><p><tt>Delete</tt> generates <tt>KB_Delete</tt> in
5309 X translations are set up to make
5310 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
5311 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
5312 is the vt220 escape code for the `delete character'
5313 key). This must be done by loading the X resources
5314 using <prgn>xrdb</prgn> on all local X displays, not
5315 using the application defaults, so that the
5316 translation resources used correspond to the
5317 <prgn>xmodmap</prgn> settings.</p></item>
5321 The Linux console is configured to make
5322 <tt><--</tt> generate DEL, and <tt>Delete</tt>
5323 generate <tt>ESC [ 3 ~</tt>.</p></item>
5327 X applications are configured so that <tt><</tt>
5328 deletes left, and <tt>Delete</tt> deletes right. Motif
5329 applications already work like this.</p></item>
5331 <item><p>Terminals should have <tt>stty erase ^?</tt> .</p></item>
5335 The <tt>xterm</tt> terminfo entry should have <tt>ESC
5336 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
5337 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.</p></item>
5341 Emacs is programmed to map <tt>KB_Backspace</tt> or
5342 the <tt>stty erase</tt> character to
5343 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
5344 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
5345 <tt>^H</tt> to <tt>help</tt> as always.</p></item>
5349 Other applications use the <tt>stty erase</tt>
5350 character and <tt>kdch1</tt> for the two delete keys,
5351 with ASCII DEL being `delete previous character' and
5352 <tt>kdch1</tt> being `delete character under
5359 This will solve the problem except for the following
5367 Some terminals have a <tt><--</tt> key that cannot
5368 be made to produce anything except <tt>^H</tt>. On
5369 these terminals Emacs help will be unavailable on
5370 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
5371 character takes precedence in Emacs, and has been set
5372 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
5373 available) can be used instead.</p></item>
5377 Some operating systems use <tt>^H</tt> for <tt>stty
5378 erase</tt>. However, modern telnet versions and all
5379 rlogin versions propagate <tt>stty</tt> settings, and
5380 almost all UNIX versions honour <tt>stty erase</tt>.
5381 Where the <tt>stty</tt> settings are not propagated
5382 correctly, things can be made to work by using
5383 <tt>stty</tt> manually.</p></item>
5387 Some systems (including previous Debian versions) use
5388 <prgn>xmodmap</prgn> to arrange for both
5389 <tt><--</tt> and <tt>Delete</tt> to generate
5390 <tt>KB_Delete</tt>. We can change the behavior of
5391 their X clients using the same X resources that we use
5392 to do it for our own clients, or configure our clients
5393 using their resources when things are the other way
5394 around. On displays configured like this
5395 <tt>Delete</tt> will not work, but <tt><--</tt>
5400 Some operating systems have different <tt>kdch1</tt>
5401 settings in their <tt>terminfo</tt> database for
5402 <tt>xterm</tt> and others. On these systems the
5403 <tt>Delete</tt> key will not work correctly when you
5404 log in from a system conforming to our policy, but
5405 <tt><--</tt> will.</p></item>
5411 <heading>Environment variables</heading>
5414 A program must not depend on environment variables to get
5415 reasonable defaults. (That's because these environment
5416 variables would have to be set in a system-wide
5417 configuration file like <file>/etc/profile</file>, which is not
5418 supported by all shells.)</p>
5421 If a program usually depends on environment variables for its
5422 configuration, the program should be changed to fall back to
5423 a reasonable default configuration if these environment
5424 variables are not present. If this cannot be done easily
5425 (e.g., if the source code of a non-free program is not
5426 available), the program must be replaced by a small
5427 `wrapper' shell script which sets the environment variables
5428 if they are not already defined, and calls the original program.</p>
5431 Here is an example of a wrapper script for this purpose:
5433 <example compact="compact">
5435 BAR=${BAR:-/var/lib/fubar}
5437 exec /usr/lib/foo/foo "$@"
5442 Furthermore, as <file>/etc/profile</file> is a configuration
5443 file of the <prgn>base-files</prgn> package, other packages must not
5444 put any environment variables or other commands into that
5450 <heading>Files</heading>
5453 <heading>Binaries</heading>
5456 Two different packages must not install programs with
5457 different functionality but with the same filenames. (The
5458 case of two programs having the same functionality but
5459 different implementations is handled via `alternatives' or
5460 the `Conflicts' mechanism. See <ref id="maintscripts"> and
5461 <ref id="conflicts"> respectively.) If this case happens,
5462 one of the programs must be renamed. The maintainers should
5463 report this to the <tt>debian-devel</tt> mailing list and
5464 try to find a consensus about which program will have to be
5465 renamed. If a consensus cannot be reached, <em>both</em>
5466 programs must be renamed.
5470 By default, when a package is being built, any binaries
5471 created should include debugging information, as well as
5472 being compiled with optimization. You should also turn on
5473 as many reasonable compilation warnings as possible; this
5474 makes life easier for porters, who can then look at build
5475 logs for possible problems. For the C programming language,
5476 this means the following compilation parameters should be
5478 <example compact="compact">
5480 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
5482 install -s # (or use strip on the files in debian/tmp)
5487 Note that by default all installed binaries should be stripped,
5488 either by using the <tt>-s</tt> flag to
5489 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
5490 the binaries after they have been copied into
5491 <file>debian/tmp</file> but before the tree is made into a
5495 Although binaries in the build tree should be compiled with
5496 debugging information by default, it can often be difficult
5497 to debug programs if they are also subjected to compiler
5498 optimization. For this reason, it is recommended to support
5499 the standardized environment
5500 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
5501 contain several flags to change how a package is compiled
5509 The presence of this string means that the package
5510 should be complied with a minimum of optimization.
5511 For C programs, it is best to add <tt>-O0</tt>
5512 to <tt>CFLAGS</tt> (although this is usually the
5513 default). Some programs might fail to build or run at
5514 this level of optimization; it may be necessary to
5515 use <tt>-O1</tt>, for example.
5521 This string means that the debugging symbols should
5522 not be stripped from the binary during installation,
5523 so that debugging information may be included in the package.
5529 The following makefile snippet is an example of how one may
5530 implement the build options; you will probably have to
5531 massage this example in order to make it work for your
5533 <example compact="compact">
5536 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
5537 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
5538 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
5539 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
5541 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
5546 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
5547 INSTALL_PROGRAM += -s
5553 It is up to the package maintainer to decide what
5554 compilation options are best for the package. Certain
5555 binaries (such as computationally-intensive programs) will
5556 function better with certain flags (<tt>-O3</tt>, for
5557 example); feel free to use them. Please use good judgment
5558 here. Don't use flags for the sake of it; only use them
5559 if there is good reason to do so. Feel free to override
5560 the upstream author's ideas about which compilation
5561 options are best: they are often inappropriate for our
5568 <heading>Libraries</heading>
5570 In general, libraries must have a shared version in the
5571 library package and a static version in the development
5572 package. The shared version must be compiled with
5573 <tt>-fPIC</tt>, and the static version must not be. In
5574 other words, each source unit ( <tt>*.c</tt>, for example,
5575 for C files) will need to be compiled twice.
5578 In some cases, it is acceptable for a library to be
5579 available in static form only; these cases include:
5582 <p>libraries for languages whose shared library support
5583 is immature or unstable</p>
5587 libraries whose interfaces are in flux or under
5588 development (commonly the case when the library's
5589 major version number is zero, or where the ABI breaks
5595 libraries which are explicitly intended to be
5596 available only in static form by their upstream
5600 If a library is available only in static form, then it must follow
5601 the conventions for a development package.
5604 All libraries must have a shared version in the
5605 <tt>lib*</tt> package and a static version in the
5606 <tt>lib*-dev</tt> package. The shared version must be
5607 compiled with <tt>-fPIC</tt>, and the static version must
5608 not be. In other words, each <tt>*.c</tt> file will need to
5609 be compiled twice.</p>
5612 You must specify the gcc option <tt>-D_REENTRANT</tt>
5613 when building a library (either static or shared) to make
5614 the library compatible with LinuxThreads.</p>
5617 Note that all installed shared libraries should be
5619 <example compact="compact">
5620 strip --strip-unneeded <var>your-lib</var>
5622 (The option <tt>--strip-unneeded</tt> makes
5623 <prgn>strip</prgn> remove only the symbols which aren't
5624 needed for relocation processing.) Shared libraries can
5625 function perfectly well when stripped, since the symbols for
5626 dynamic linking are in a separate part of the ELF object
5629 You might also want to use the options
5630 <tt>--remove-section=.comment</tt> and
5631 <tt>--remove-section=.note</tt> on both shared libraries
5632 and executables, and <tt>--strip-debug</tt> on static
5639 Note that under some circumstances it may be useful to
5640 install a shared library unstripped, for example when
5641 building a separate package to support debugging.
5645 Shared object files (often <file>.so</file> files) that are not
5646 public libraries, that is, they are not meant to be linked
5647 to by third party executables (binaries of other packages),
5648 should be installed in subdirectories of the
5649 <file>/usr/lib</file> directory. Such files are exempt from the
5650 rules that govern ordinary shared libraries, except that
5651 they must not be installed executable and should be
5654 A common example are the so-called ``plug-ins'',
5655 internal shared objects that are dynamically loaded by
5656 programs using <manref name="dlopen" section="3">.
5662 Packages containing shared libraries that may be linked to
5663 by other packages' binaries, but which for some
5664 <em>compelling</em> reason can not be installed in
5665 <file>/usr/lib</file> directory, may install the shared library
5666 files in subdirectories of the <file>/usr/lib</file> directory,
5667 in which case they should arrange to add that directory in
5668 <file>/etc/ld.so.conf</file> in the package's post-installation
5669 script, and remove it in the package's post-removal script.
5673 An ever increasing number of packages are using
5674 <prgn>libtool</prgn> to do their linking. The latest GNU
5675 libtools (>= 1.3a) can take advantage of the metadata in the
5676 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
5677 files). The main advantage of <prgn>libtool</prgn>'s
5678 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
5679 store and subsequently access metadata with respect to the
5680 libraries it builds. <prgn>libtool</prgn> will search for
5681 those files, which contain a lot of useful information about
5682 a library (such as library dependency information for static
5683 linking). Also, they're <em>essential</em> for programs
5684 using <tt>libltdl</tt>.<footnote>
5686 Although <prgn>libtool</prgn> is fully capable of
5687 linking against shared libraries which don't have
5688 <tt>.la</tt> files, as it is a mere shell script it can
5689 add considerably to the build time of a
5690 <prgn>libtool</prgn>-using package if that shell script
5691 has to derive all this information from first principles
5692 for each library every time it is linked. With the
5693 advent of <prgn>libtool</prgn> version 1.4 (and to a
5694 lesser extent <prgn>libtool</prgn> version 1.3), the
5695 <file>.la</file> files also store information about
5696 inter-library dependencies which cannot necessarily be
5697 derived after the <file>.la</file> file is deleted.
5703 Packages that use <prgn>libtool</prgn> to create shared
5704 libraries should include the <file>.la</file> files in the
5705 <tt>-dev</tt> package, unless the package relies on
5706 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
5707 the <tt>.la</tt> files must go in the run-time library
5712 You must make sure that you use only released versions of
5713 shared libraries to build your packages; otherwise other
5714 users will not be able to run your binaries
5715 properly. Producing source packages that depend on
5716 unreleased compilers is also usually a bad
5722 <heading>Shared libraries</heading>
5725 Packages involving shared libraries should be split up
5726 into several binary packages.</p>
5729 For a straightforward library which has a development
5730 environment and a runtime kit including just shared
5731 libraries you need to create two packages:
5732 <file><var>libraryname</var><var>soversion</var></file>, where
5733 <file><var>soversion</var></file> is the version number in the
5734 soname of the shared library<footnote>
5736 The soname is the shared object name: it's the thing
5737 that has to match exactly between building an executable
5738 and running it for the dynamic linker to be able run the
5739 program. For example, if the soname of the library is
5740 <file>libfoo.so.6</file>, the library package would be
5741 called <file>libfoo6</file>.
5744 and <tt><var>libraryname</var><var>soversion</var>-dev</tt>.
5745 Alternatively, if it would be confusing to directly append
5746 <var>soversion</var> to <var>libraryname</var> (e.g. because
5747 <var>libraryname</var> itself ends in a number), you may use
5748 <tt><var>libraryname</var>-<var>soversion</var></tt> and
5749 <tt><var>libraryname</var>-<var>soversion</var>-dev</tt>
5754 If you prefer only to support one development version at a
5755 time you may name the development package
5756 <file><var>libraryname</var>-dev</file>; otherwise you may need
5757 to use <prgn>dpkg</prgn>'s Conflicts mechanism (see <ref
5758 id="conflicts">) to ensure that the user only installs one
5759 development version at a time (as different development
5760 versions are likely to have the same header files in them,
5761 which would cause a filename clash if both were installed).
5762 Typically the development version should also have an exact
5763 version dependency on the runtime library, to make sure that
5764 compilation and linking happens correctly. The
5765 <tt>${Source-Version}</tt> substitution variable can be
5766 useful for this purpose.
5770 Packages which use the shared library should have a
5771 dependency on the name of the shared library package,
5772 <file><var>libraryname</var><var>soversion</var></file>. When
5773 the soname changes you can have both versions of the library
5774 installed while migrating from the old library to the new.
5778 If your package has some run-time support programs which use
5779 the shared library you must not put them in the shared
5780 library package. If you do that then you won't be able to
5781 install several versions of the shared library without
5782 getting filename clashes. Instead, either create a third
5783 package for the runtime binaries (this package might
5784 typically be named <tt><var>libraryname</var>-runtime</tt>;
5785 note the absence of the <var>soversion</var> in the package
5786 name), or if the development package is small you may
5787 include them in there.
5791 If you have several shared libraries built from the same
5792 source tree you may lump them all together into a single
5793 shared library package, provided that you change all of
5794 their sonames at once (so that you don't get filename
5795 clashes if you try to install different versions of the
5796 combined shared libraries package).
5800 Shared libraries should not be installed executable, since
5801 the dynamic linker does not require this and trying to
5802 execute a shared library usually results in a core dump.
5807 <heading>Scripts</heading>
5810 All command scripts, including the package maintainer
5811 scripts inside the package and used by <prgn>dpkg</prgn>,
5812 should have a <tt>#!</tt> line naming the shell to be used
5813 to interpret them.</p>
5816 In the case of Perl scripts this should be
5817 <tt>#!/usr/bin/perl</tt>.</p>
5820 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
5821 should almost certainly start with <tt>set -e</tt> so that
5822 errors are detected. Every script should use
5823 <tt>set -e</tt> or check the exit status of <em>every</em>
5827 The standard shell interpreter <file>/bin/sh</file> can be a
5828 symbolic link to any POSIX compatible shell, if <tt>echo
5829 -n</tt> does not generate a newline.<footnote>
5831 Debian policy specifies POSIX behavior for
5832 <file>/bin/sh</file>, but <tt>echo -n</tt> has widespread
5833 use in the Linux community (in particular including this
5834 policy, the Linux kernel source, many Debian scripts,
5835 etc.). This <tt>echo -n</tt> mechanism is valid but not
5836 required under POSIX, hence this explicit addition.
5837 Also, rumour has it that this shall be mandated under
5841 Thus, shell scripts specifying <file>/bin/sh</file> as
5842 interpreter should only use POSIX features. If a script
5843 requires non-POSIX features from the shell interpreter, the
5844 appropriate shell must be specified in the first line of the
5845 script (e.g., <tt>#!/bin/bash</tt>) and the package must
5846 depend on the package providing the shell (unless the shell
5847 package is marked `Essential', as in the case of
5852 You may wish to restrict your script to POSIX features when
5853 possible so that it may use <file>/bin/sh</file> as its
5854 interpreter. If your script works with <prgn>dash</prgn>
5855 (originally called <prgn>ash</prgn>), it's probably POSIX
5856 compliant, but if you are in doubt, use
5857 <file>/bin/bash</file>.
5861 Perl scripts should check for errors when making any
5862 system calls, including <tt>open</tt>, <tt>print</tt>,
5863 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
5867 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
5868 scripting languages. See <em>Csh Programming Considered
5869 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
5870 can be found at <url
5871 id="http://language.perl.com/versus/csh.whynot">.<footnote>
5873 It can also be found on
5874 <url id="http://www.cpan.org/doc/FMTEYEWTK/versus/csh.whynot">
5875 or on the ftp site <ftpsite>ftp.cpan.org</ftpsite> as
5876 <ftppath>/pub/perl/CPAN/doc/FMTEYEWTK/versus/csh.whynot</ftppath>.
5879 If an upstream package comes with <prgn>csh</prgn> scripts
5880 then you must make sure that they start with
5881 <tt>#!/bin/csh</tt> and make your package depend on the
5882 <prgn>c-shell</prgn> virtual package.
5886 Any scripts which create files in world-writeable
5887 directories (e.g., in <file>/tmp</file>) must use a
5888 mechanism which will fail if a file with the same name
5892 The Debian base system provides the <prgn>tempfile</prgn>
5893 and <prgn>mktemp</prgn> utilities for use by scripts for
5894 this purpose.</p></sect>
5898 <heading>Symbolic links</heading>
5901 In general, symbolic links within a top-level directory
5902 should be relative, and symbolic links pointing from one
5903 top-level directory into another should be absolute. (A
5904 top-level directory is a sub-directory of the root
5905 directory <file>/</file>.)</p>
5908 In addition, symbolic links should be specified as short as
5909 possible, i.e., link targets like <file>foo/../bar</file> are
5913 Note that when creating a relative link using
5914 <prgn>ln</prgn> it is not necessary for the target of the
5915 link to exist relative to the working directory you're
5916 running <prgn>ln</prgn> from, nor is it necessary to change
5917 directory to the directory where the link is to be made.
5918 Simply include the string that should appear as the target
5919 of the link (this will be a pathname relative to the
5920 directory in which the link resides) as the first argument
5921 to <prgn>ln</prgn>.</p>
5924 For example, in your <prgn>Makefile</prgn> or
5925 <file>debian/rules</file>, you can do things like:
5926 <example compact="compact">
5927 ln -fs gcc $(prefix)/bin/cc
5928 ln -fs gcc debian/tmp/usr/bin/cc
5929 ln -fs ../sbin/sendmail $(prefix)/bin/runq
5930 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
5934 A symbolic link pointing to a compressed file should always
5935 have the same file extension as the referenced file. (For
5936 example, if a file <file>foo.gz</file> is referenced by a
5937 symbolic link, the filename of the link has to end with
5938 `<file>.gz</file>' too, as in <file>bar.gz</file>.)
5943 <heading>Device files</heading>
5946 Packages must not include device files in the package file
5950 If a package needs any special device files that are not
5951 included in the base system, it must call
5952 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
5953 after notifying the user<footnote>
5955 This notification could be done via a (low-priority)
5956 debconf message, or an echo (printf) statement.
5962 Packages must not remove any device files in the
5963 <prgn>postrm</prgn> or any other script. This is left to the
5964 system administrator.</p>
5967 Debian uses the serial devices
5968 <file>/dev/ttyS*</file>. Programs using the old
5969 <file>/dev/cu*</file> devices should be changed to use
5970 <file>/dev/ttyS*</file>.</p>
5973 <sect id="config-files">
5974 <heading>Configuration files</heading>
5976 <heading>Definitions</heading>
5979 <tag>configuration file</tag>
5982 A file that affects the operation of a program, or
5983 provides site- or host-specific information, or
5984 otherwise customizes the behavior of a program.
5985 Typically, configuration files are intended to be
5986 modified by the system administrator (if needed or
5987 desired) to conform to local policy or to provide
5988 more useful site-specific behavior.
5992 <tag><tt>conffile</tt></tag>
5995 A file listed in a package's <tt>conffiles</tt>
5996 file, and is treated specially by <prgn>dpkg</prgn>
5997 (see <ref id="configdetails">).
6004 The distinction between these two is important; they are
6005 not interchangeable concepts. Almost all
6006 <tt>conffile</tt>s are configuration files, but many
6007 configuration files are not <tt>conffiles</tt>.
6011 Note that a script that embeds configuration information
6012 (such as most of the files in <file>/etc/default</file> and
6013 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6014 configuration file and should be treated as such.
6019 <heading>Location</heading>
6021 Any configuration files created or used by your package
6022 must reside in <file>/etc</file>. If there are several you
6023 should consider creating a subdirectory of <file>/etc</file>
6024 named after your package.</p>
6027 If your package creates or uses configuration files
6028 outside of <file>/etc</file>, and it is not feasible to modify
6029 the package to use the <file>/etc</file>, you should still put
6030 the files in <file>/etc</file> and create symbolic links to
6031 those files from the location that the package
6036 <heading>Behavior</heading>
6038 Configuration file handling must conform to the following
6040 <list compact="compact">
6043 local changes must be preserved during a package
6049 configuration files must be preserved when the
6050 package is removed, and only deleted when the
6058 The easy way to achieve this behavior is to make the
6059 configuration file a <tt>conffile</tt>. This is
6060 appropriate only if it is possible to distribute a default
6061 version that will work for most installations, although
6062 some system administrators may choose to modify it. This
6063 implies that the default version will be part of the
6064 package distribution, and must not be modified by the
6065 maintainer scripts during installation (or at any other
6070 In order to ensure that local changes are preserved
6071 correctly, no package may contain or make hard links to
6072 conffiles.<footnote>
6074 Rationale: There are two problems with hard links.
6075 The first is that some editors break the link while
6076 editing one of the files, so that the two files may
6077 unwittingly become unlinked and different. The second
6078 is that <prgn>dpkg</prgn> might break the hard link
6079 while upgrading <tt>conffile</tt>s.
6085 The other way to do it is via the maintainer scripts. In
6086 this case, the configuration file must not be listed as a
6087 <tt>conffile</tt> and must not be part of the package
6088 distribution. If the existence of a file is required for
6089 the package to be sensibly configured it is the
6090 responsibility of the package maintainer to provide
6091 maintainer scripts which correctly create, update and
6092 maintain the file and remove it on purge. (See <ref
6093 id="maintainerscripts"> for more information.) These
6094 scripts must be idempotent (i.e., must work correctly if
6095 <prgn>dpkg</prgn> needs to re-run them due to errors
6096 during installation or removal), must cope with all the
6097 variety of ways <prgn>dpkg</prgn> can call maintainer
6098 scripts, must not overwrite or otherwise mangle the user's
6099 configuration without asking, must not ask unnecessary
6100 questions (particularly during upgrades), and otherwise be
6105 The scripts are not required to configure every possible
6106 option for the package, but only those necessary to get
6107 the package running on a given system. Ideally the
6108 sysadmin should not have to do any configuration other
6109 than that done (semi-)automatically by the
6110 <prgn>postinst</prgn> script.
6114 A common practice is to create a script called
6115 <file><var>package</var>-configure</file> and have the
6116 package's <prgn>postinst</prgn> call it if and only if the
6117 configuration file does not already exist. In certain
6118 cases it is useful for there to be an example or template
6119 file which the maintainer scripts use. Such files should
6120 be in <file>/usr/share/<var>package</var></file> or
6121 <file>/usr/lib/<var>package</var></file> (depending on whether
6122 they are architecture-independent or not). There should
6123 be symbolic links to them from
6124 <file>/usr/share/doc/<var>package</var>/examples</file> if
6125 they are examples, and should be perfectly ordinary
6126 <prgn>dpkg</prgn>-handled files (<em>not</em>
6127 configuration files).
6131 These two styles of configuration file handling must
6132 not be mixed, for that way lies madness:
6133 <prgn>dpkg</prgn> will ask about overwriting the file
6134 every time the package is upgraded.
6139 <heading>Sharing configuration files</heading>
6141 Packages which specify the same file as a
6142 <tt>conffile</tt> must be tagged as <em>conflicting</em>
6143 with each other. (This is an instance of the general rule
6144 about not sharing files. Note that neither alternatives
6145 nor diversions are likely to be appropriate in this case;
6146 in particular, <prgn>dpkg</prgn> does not handle diverted
6147 <tt>conffile</tt>s well.)
6151 The maintainer scripts must not alter a <tt>conffile</tt>
6152 of <em>any</em> package, including the one the scripts
6157 If two or more packages use the same configuration file
6158 and it is reasonable for both to be installed at the same
6159 time, one of these packages must be defined as
6160 <em>owner</em> of the configuration file, i.e., it will be
6161 the package which handles that file as a configuration
6162 file. Other packages that use the configuration file must
6163 depend on the owning package if they require the
6164 configuration file to operate. If the other package will
6165 use the configuration file if present, but is capable of
6166 operating without it, no dependency need be declared.</p>
6169 If it is desirable for two or more related packages to
6170 share a configuration file <em>and</em> for all of the
6171 related packages to be able to modify that configuration
6172 file, then the following should be done:
6173 <enumlist compact="compact">
6176 One of the related packages (the "owning" package)
6177 will manage the configuration file with maintainer
6178 scripts as described in the previous section.
6183 The owning package should also provide a program
6184 that the other packages may use to modify the
6190 The related packages must use the provided program
6191 to make any desired modifications to the
6192 configuration file. They should either depend on
6193 the core package to guarantee that the configuration
6194 modifier program is available or accept gracefully
6195 that they cannot modify the configuration file if it
6196 is not. (This is in addition to the fact that the
6197 configuration file may not even be present in the
6205 Sometimes it's appropriate to create a new package which
6206 provides the basic infrastructure for the other packages
6207 and which manages the shared configuration files. (The
6208 <tt>sgml-base</tt> package is a good example.)
6213 <heading>User configuration files ("dotfiles")</heading>
6216 The files in <file>/etc/skel</file> will automatically be
6217 copied into new user accounts by <prgn>adduser</prgn>.
6218 No other program should reference the files in
6219 <file>/etc/skel</file>.
6223 Therefore, if a program needs a dotfile to exist in
6224 advance in <file>$HOME</file> to work sensibly, that dotfile
6225 should be installed in <file>/etc/skel</file> and treated as a
6230 However, programs that require dotfiles in order to
6231 operate sensibly (dotfiles that they do not create
6232 themselves automatically, that is) are a bad thing.
6233 Furthermore, programs should be configured by the Debian
6234 default installation to behave as closely to the upstream
6235 default behaviour as possible.
6239 Therefore, if a program in a Debian package needs to be
6240 configured in some way in order to operate sensibly, that
6241 should be done using a site-wide configuration file placed
6242 in <file>/etc</file>. Only if the program doesn't support a
6243 site-wide default configuration and the package maintainer
6244 doesn't have time to add it may a default per-user file be
6245 placed in <file>/etc/skel</file>.
6249 <file>/etc/skel</file> should be as empty as we can make it.
6250 This is particularly true because there is no easy (or
6251 necessarily desirable) mechanism for ensuring that the
6252 appropriate dotfiles are copied into the accounts of
6253 existing users when a package is installed.
6259 <heading>Log files</heading>
6261 Log files should usually be named
6262 <file>/var/log/<var>package</var>.log</file>. If you have many
6263 log files, or need a separate directory for permission
6264 reasons (<file>/var/log</file> is writable only by
6265 <file>root</file>), you should usually create a directory named
6266 <file>/var/log/<var>package</var></file> and place your log
6271 Log files must be rotated occasionally so that they don't
6272 grow indefinitely; the best way to do this is to drop a log
6273 rotation configuration file into the directory
6274 <file>/etc/logrotate.d</file> and use the facilities provided by
6275 logrotate.<footnote>
6277 The traditional approach to log files has been to set up
6278 <em>ad hoc</em> log rotation schemes using simple shell
6279 scripts and cron. While this approach is highly
6280 customizable, it requires quite a lot of sysadmin work.
6281 Even though the original Debian system helped a little
6282 by automatically installing a system which can be used
6283 as a template, this was deemed not enough.
6287 The use of <prgn>logrotate</prgn>, a program developed
6288 by Red Hat, is better, as it centralizes log management.
6289 It has both a configuration file
6290 (<file>/etc/logrotate.conf</file>) and a directory where
6291 packages can drop their individual log rotation
6292 configurations (<file>/etc/logrotate.d</file>).
6295 Here is a good example for a logrotate config
6296 file (for more information see <manref name="logrotate"
6298 <example compact="compact">
6304 /etc/init.d/foo force-reload
6308 This rotates all files under <file>/var/log/foo</file>, saves 12
6309 compressed generations, and forces the daemon to reload its
6310 configuration information after the log rotation.
6314 Log files should be removed when the package is
6315 purged (but not when it is only removed). This should be
6316 done by the <prgn>postrm</prgn> script when it is called
6317 with the argument <tt>purge</tt> (see <ref
6318 id="removedetails">).
6323 <heading>Permissions and owners</heading>
6326 The rules in this section are guidelines for general use.
6327 If necessary you may deviate from the details below.
6328 However, if you do so you must make sure that what is done
6329 is secure and you should try to be as consistent as possible
6330 with the rest of the system. You should probably also
6331 discuss it on <prgn>debian-devel</prgn> first.
6335 Files should be owned by <tt>root.root</tt>, and made
6336 writable only by the owner and universally readable (and
6337 executable, if appropriate), that is mode 644 or 755.
6341 Directories should be mode 755 or (for group-writability)
6342 mode 2775. The ownership of the directory should be
6343 consistent with its mode: if a directory is mode 2775, it
6344 should be owned by the group that needs write access to
6349 Setuid and setgid executables should be mode 4755 or 2755
6350 respectively, and owned by the appropriate user or group.
6351 They should not be made unreadable (modes like 4711 or
6352 2711 or even 4111); doing so achieves no extra security,
6353 because anyone can find the binary in the freely available
6354 Debian package; it is merely inconvenient. For the same
6355 reason you should not restrict read or execute permissions
6356 on non-set-id executables.
6360 Some setuid programs need to be restricted to particular
6361 sets of users, using file permissions. In this case they
6362 should be owned by the uid to which they are set-id, and by
6363 the group which should be allowed to execute them. They
6364 should have mode 4754; again there is no point in making
6365 them unreadable to those users who must not be allowed to
6370 It is possible to arrange that the system administrator can
6371 reconfigure the package to correspond to their local
6372 security policy by changing the permissions on a binary:
6373 they can do this by using <prgn>dpkg-statoverride</prgn>, as
6374 described below.<footnote>
6376 Ordinary files installed by <prgn>dpkg</prgn> (as
6377 opposed to <tt>conffile</tt>s and other similar objects)
6378 normally have their permissions reset to the distributed
6379 permissions when the package is reinstalled. However,
6380 the use of <prgn>dpkg-statoverride</prgn> overrides this
6381 default behaviour. If you use this method, you should
6382 remember to describe <prgn>dpkg-statoverride</prgn> in
6383 the package documentation; being a relatively new
6384 addition to Debian, it is probably not yet well-known.
6387 Another method you should consider is to create a group for
6388 people allowed to use the program(s) and make any setuid
6389 executables executable only by that group.
6393 If you need to create a new user or group for your package
6394 there are two possibilities. Firstly, you may need to
6395 make some files in the binary package be owned by this
6396 user or group, or you may need to compile the user or
6397 group id (rather than just the name) into the binary
6398 (though this latter should be avoided if possible, as in
6399 this case you need a statically allocated id).</p>
6402 If you need a statically allocated id, you must ask for a
6403 user or group id from the <tt>base-passwd</tt> maintainer,
6404 and must not release the package until you have been
6405 allocated one. Once you have been allocated one you must
6406 either make the package depend on a version of the
6407 <tt>base-passwd</tt> package with the id present in
6408 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
6409 your package to create the user or group itself with the
6410 correct id (using <tt>adduser</tt>) in its
6411 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
6412 the <prgn>postinst</prgn> is to be preferred if it is
6413 possible, otherwise a pre-dependency will be needed on the
6414 <tt>adduser</tt> package.)
6418 On the other hand, the program might be able to determine
6419 the uid or gid from the user or group name at runtime, so
6420 that a dynamically allocated id can be used. In this case
6421 you should choose an appropriate user or group name,
6422 discussing this on <prgn>debian-devel</prgn> and checking
6423 with the base system maintainer that it is unique and that
6424 they do not wish you to use a statically allocated id
6425 instead. When this has been checked you must arrange for
6426 your package to create the user or group if necessary using
6427 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
6428 <prgn>postinst</prgn> script (again, the latter is to be
6429 preferred if it is possible).
6433 Note that changing the numeric value of an id associated
6434 with a name is very difficult, and involves searching the
6435 file system for all appropriate files. You need to think
6436 carefully whether a static or dynamic id is required, since
6437 changing your mind later will cause problems.
6440 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
6442 This section is not intended as policy, but as a
6443 description of the use of <prgn>dpkg-statoverride</prgn>.
6447 <prgn>dpkg-statoverride</prgn> is a replacement for the
6448 deprecated <tt>suidmanager</tt> package. Packages which
6449 previously used <tt>suidmanager</tt> should have a
6450 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
6451 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
6452 and <tt>suidunregister</tt> should now be simply removed
6453 from the maintainer scripts.
6457 If a system administrator wishes to have a file (or
6458 directory or other such thing) installed with owner and
6459 permissions different from those in the distributed Debian
6460 package, he can use the <prgn>dpkg-statoverride</prgn>
6461 program to instruct <prgn>dpkg</prgn> to use the different
6462 settings every time the file is installed. Thus the
6463 package maintainer should distribute the files with their
6464 normal permissions, and leave it for the system
6465 administrator to make any desired changes. For example, a
6466 daemon which is normally required to be setuid root, but
6467 in certain situations could be used without being setuid,
6468 should be installed setuid in the <tt>.deb</tt>. Then the
6469 local system administrator can change this if they wish.
6470 If there are two standard ways of doing it, the package
6471 maintainer can use <tt>debconf</tt> to find out the
6472 preference, and call <prgn>dpkg-statoverride</prgn> in the
6473 maintainer script if necessary to accommodate the system
6474 administrator's choice.
6478 Given the above, <prgn>dpkg-statoverride</prgn> is
6479 essentially a tool for system administrators and would not
6480 normally be needed in the maintainer scripts. There is
6481 one type of situation, though, where calls to
6482 <prgn>dpkg-statoverride</prgn> would be needed in the
6483 maintainer scripts, and that involves packages which use
6484 dynamically allocated user or group ids. In such a
6485 situation, something like the following idiom can be very
6486 helpful in the package's <prgn>postinst</prgn>, where
6487 <tt>sysuser</tt> is a dynamically allocated id:
6489 for i in /usr/bin/foo /usr/sbin/bar
6491 if ! dpkg-statoverride --list $i >/dev/null
6493 dpkg-statoverride --update --add sysuser root 4755 $i
6497 The corresponding <tt>dpkg-statoverride --remove</tt>
6498 calls can then be made unconditionally when the package is
6505 <chapt id="customized-programs">
6506 <heading>Customized programs</heading>
6508 <sect id="arch-spec">
6509 <heading>Architecture specification strings</heading>
6512 If a program needs to specify an <em>architecture specification
6513 string</em> in some place, the following format should be
6514 used: <var>arch</var>-<var>os</var><footnote>
6516 The following architectures and operating systems are
6517 currently recognised by <prgn>dpkg-archictecture</prgn>.
6518 The architecture, <tt><var>arch</var></tt>, is one of
6519 the following: <tt>alpha</tt>, <tt>arm</tt>,
6520 <tt>hppa</tt>, <tt>i386</tt>, <tt>ia64</tt>,
6521 <tt>m68k</tt>, <tt>mips</tt>, <tt>mipsel</tt>,
6522 <tt>powerpc</tt>, <tt>s390</tt>, <tt>sh</tt>,
6523 <tt>sheb</tt>, <tt>sparc</tt> and <tt>sparc64</tt>. The
6524 operating system, <tt><var>os</var></tt>, is one of:
6525 <tt>linux</tt>, <tt>gnu</tt>, <tt>freebsd</tt> and
6526 <tt>openbsd</tt>. Use of <tt>gnu</tt> in this string is
6527 reserved for the GNU/Hurd operating system.
6533 Note that we don't want to use
6534 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
6535 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
6536 since this would make our programs incompatible with other
6537 Linux distributions. We also don't use something like
6538 <tt><var>arch</var>-unknown-linux</tt>, since the
6539 <tt>unknown</tt> does not look very good.
6544 <heading>Daemons</heading>
6547 The configuration files <file>/etc/services</file>,
6548 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
6549 by the <prgn>netbase</prgn> package and must not be modified
6554 If a package requires a new entry in one of these files, the
6555 maintainer should get in contact with the
6556 <prgn>netbase</prgn> maintainer, who will add the entries
6557 and release a new version of the <prgn>netbase</prgn>
6562 The configuration file <file>/etc/inetd.conf</file> must not be
6563 modified by the package's scripts except via the
6564 <prgn>update-inetd</prgn> script or the
6565 <file>DebianNet.pm</file> Perl module. See their documentation
6566 for details on how to add entries.
6570 If a package wants to install an example entry into
6571 <file>/etc/inetd.conf</file>, the entry must be preceded with
6572 exactly one hash character (<tt>#</tt>). Such lines are
6573 treated as `commented out by user' by the
6574 <prgn>update-inetd</prgn> script and are not changed or
6575 activated during package updates.
6580 <heading>Using pseudo-ttys and modifying wtmp, utmp and
6584 Some programs need to create pseudo-ttys. This should be done
6585 using Unix98 ptys if the C library supports it. The resulting
6586 program must not be installed setuid root, unless that
6587 is required for other functionality.
6591 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
6592 <file>/var/log/lastlog</file> must be installed writeable by
6593 group <tt>utmp</tt>. Programs which need to modify those
6594 files must be installed setgid <tt>utmp</tt>.
6599 <heading>Editors and pagers</heading>
6602 Some programs have the ability to launch an editor or pager
6603 program to edit or display a text document. Since there are
6604 lots of different editors and pagers available in the Debian
6605 distribution, the system administrator and each user should
6606 have the possibility to choose his/her preferred editor and
6611 In addition, every program should choose a good default
6612 editor/pager if none is selected by the user or system
6617 Thus, every program that launches an editor or pager must
6618 use the EDITOR or PAGER environment variable to determine
6619 the editor or pager the user wishes to use. If these
6620 variables are not set, the programs <file>/usr/bin/editor</file>
6621 and <file>/usr/bin/pager</file> should be used, respectively.
6625 These two files are managed through the <prgn>dpkg</prgn>
6626 `alternatives' mechanism. Thus every package providing an
6627 editor or pager must call the
6628 <prgn>update-alternatives</prgn> script to register these
6633 If it is very hard to adapt a program to make use of the
6634 EDITOR or PAGER variables, that program may be configured to
6635 use <file>/usr/bin/sensible-editor</file> and
6636 <file>/usr/bin/sensible-pager</file> as the editor or pager
6637 program respectively. These are two scripts provided in the
6638 Debian base system that check the EDITOR and PAGER variables
6639 and launch the appropriate program, and fall back to
6640 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
6641 variable is not set.
6645 A program may also use the VISUAL environment variable to
6646 determine the user's choice of editor. If it exists, it
6647 should take precedence over EDITOR. This is in fact what
6648 <file>/usr/bin/sensible-editor</file> does.
6652 It is not required for a package to depend on
6653 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
6654 package to provide such virtual packages.<footnote>
6656 The Debian base system already provides an editor and a
6663 <sect id="web-appl">
6664 <heading>Web servers and applications</heading>
6667 This section describes the locations and URLs that should
6668 be used by all web servers and web applications in the
6676 Cgi-bin executable files are installed in the
6678 <example compact="compact">
6679 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
6681 and should be referred to as
6682 <example compact="compact">
6683 http://localhost/cgi-bin/<var>cgi-bin-name</var>
6688 <item><p>Access to HTML documents</p>
6691 HTML documents for a package are stored in
6692 <file>/usr/share/doc/<var>package</var></file>
6693 and can be referred to as
6694 <example compact="compact">
6695 http://localhost/doc/<var>package</var>/<var>filename</var>
6699 The web server should restrict access to the document
6700 tree so that only clients on the same host can read
6701 the documents. If the web server does not support such
6702 access controls, then it should not provide access at
6703 all, or ask about providing access during installation.
6707 <item><p>Web Document Root</p>
6710 Web Applications should try to avoid storing files in
6711 the Web Document Root. Instead they should use the
6712 /usr/share/doc/<var>package</var> directory for
6713 documents and register the Web Application via the
6714 menu package. If access to the web document root is
6715 unavoidable then use
6716 <example compact="compact">
6719 as the Document Root. This might be just a symbolic
6720 link to the location where the system administrator
6721 has put the real document root.
6725 </enumlist></p></sect>
6728 <sect id="mail-transport-agents">
6729 <heading>Mail transport, delivery and user agents</heading>
6732 Debian packages which process electronic mail, whether mail
6733 user agents (MUAs) or mail transport agents (MTAs), must
6734 ensure that they are compatible with the configuration
6735 decisions below. Failure to do this may result in lost
6736 mail, broken <tt>From:</tt> lines, and other serious brain
6741 The mail spool is <file>/var/mail</file> and the interface to
6742 send a mail message is <file>/usr/sbin/sendmail</file> (as per
6743 the FHS). On older systems, the mail spool may be
6744 physically located in <file>/var/spool/mail</file>, but all
6745 access to the mail spool should be via the
6746 <file>/var/mail</file> symlink. The mail spool is part of the
6747 base system and not part of the MTA package.
6751 All Debian MUAs, MTAs, MDAs and other mailbox accessing
6752 programs (such as IMAP daemons) must lock the mailbox in an
6753 NFS-safe way. This means that <tt>fcntl()</tt> locking must
6754 be combined with dot locking. To avoid deadlocks, a program
6755 should use <tt>fcntl()</tt> first and dot locking after
6756 this, or alternatively implement the two locking methods in
6757 a non blocking way<footnote>
6759 If it is not possible to establish both locks, the
6760 system shouldn't wait for the second lock to be
6761 established, but remove the first lock, wait a (random)
6762 time, and start over locking again.
6764 </footnote>. Using the functions <tt>maillock</tt> and
6765 <tt>mailunlock</tt> provided by the
6766 <tt>liblockfile*</tt><footnote>
6768 You will need to depend on <tt>liblockfile1
6769 (>>1.01)</tt> to use these functions.
6771 </footnote> packages is the recommended way to realize this.
6775 Mailboxes are generally mode 660
6776 <tt><var>user</var>.mail</tt> unless the system
6777 administrator has chosen otherwise. A MUA may remove a
6778 mailbox (unless it has nonstandard permissions) in which
6779 case the MTA or another MUA must recreate it if needed.
6780 Mailboxes must be writable by group mail.
6784 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
6785 be setgid mail to do the locking mentioned above (and
6786 must obviously avoid accessing other users' mailboxes
6787 using this privilege).</p>
6790 <file>/etc/aliases</file> is the source file for the system mail
6791 aliases (e.g., postmaster, usenet, etc.), it is the one
6792 which the sysadmin and <prgn>postinst</prgn> scripts may
6793 edit. After <file>/etc/aliases</file> is edited the program or
6794 human editing it must call <prgn>newaliases</prgn>. All MTA
6795 packages must come with a <prgn>newaliases</prgn> program,
6796 even if it does nothing, but older MTA packages did not do
6797 this so programs should not fail if <prgn>newaliases</prgn>
6798 cannot be found. Note that because of this, all MTA
6799 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
6800 <tt>Replaces: mail-transport-agent</tt> control file
6805 The convention of writing <tt>forward to
6806 <var>address</var></tt> in the mailbox itself is not
6807 supported. Use a <tt>.forward</tt> file instead.</p>
6810 The <prgn>rmail</prgn> program used by UUCP
6811 for incoming mail should be <file>/usr/sbin/rmail</file>.
6812 Likewise, <prgn>rsmtp</prgn>, for receiving
6813 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
6817 If your package needs to know what hostname to use on (for
6818 example) outgoing news and mail messages which are generated
6819 locally, you should use the file <file>/etc/mailname</file>. It
6820 will contain the portion after the username and <tt>@</tt>
6821 (at) sign for email addresses of users on the machine
6822 (followed by a newline).
6826 Such package should check for the existence of this file
6827 when it is being configured. If it exists, it should be
6828 used without comment, although an MTA's configuration script
6829 may wish to prompt the user even if it finds that this file
6830 exists. If the file does not exist, the package should
6831 prompt the user for the value (preferably using
6832 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
6833 as well as using it in the package's configuration. The
6834 prompt should make it clear that the name will not just be
6835 used by that package. For example, in this situation the
6836 <tt>inn</tt> package could say something like:
6837 <example compact="compact">
6838 Please enter the `mail name' of your system. This is the
6839 hostname portion of the address to be shown on outgoing
6840 news and mail messages. The default is
6841 <var>syshostname</var>, your system's host name. Mail
6842 name [`<var>syshostname</var>']:
6844 where <var>syshostname</var> is the output of <tt>hostname
6850 <heading>News system configuration</heading>
6853 All the configuration files related to the NNTP (news)
6854 servers and clients should be located under
6855 <file>/etc/news</file>.</p>
6858 There are some configuration issues that apply to a number
6859 of news clients and server packages on the machine. These
6863 <tag><file>/etc/news/organization</file></tag>
6864 <item><p>A string which should appear as the
6865 organization header for all messages posted
6866 by NNTP clients on the machine</p></item>
6868 <tag><file>/etc/news/server</file></tag>
6869 <item><p>Contains the FQDN of the upstream NNTP
6870 server, or localhost if the local machine is
6871 an NNTP server.</p></item>
6874 Other global files may be added as required for cross-package news
6875 configuration.</p></sect>
6879 <heading>Programs for the X Window System</heading>
6882 <heading>Providing X support and package priorities</heading>
6885 Programs that can be configured with support for the X
6886 Window System must be configured to do so and must declare
6887 any package dependencies necessary to satisfy their
6888 runtime requirements when using the X Window System. If
6889 such a package is of higher priority than the X packages
6890 on which it depends, it is required that either the
6891 X-specific components be split into a separate package, or
6892 that an alternative version of the package, which includes
6893 X support, be provided, or that the package's priority be
6899 <heading>Packages providing an X server</heading>
6902 Packages that provide an X server that, directly or
6903 indirectly, communicates with real input and display
6904 hardware should declare in their control data that they
6905 provide the virtual package <tt>xserver</tt>.<footnote>
6907 This implements current practice, and provides an
6908 actual policy for usage of the <tt>xserver</tt>
6909 virtual package which appears in the virtual packages
6910 list. In a nutshell, X servers that interface
6911 directly with the display and input hardware or via
6912 another subsystem (e.g., GGI) should provide
6913 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
6914 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
6921 <heading>Packages providing a terminal emulator</heading>
6924 Packages that provide a terminal emulator for the X Window
6925 System which meet the criteria listed below should declare
6926 in their control data that they provide the virtual
6927 package <tt>x-terminal-emulator</tt>. They should also
6928 register themselves as an alternative for
6929 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
6934 To be an <tt>x-terminal-emulator</tt>, a program must:
6935 <list compact="compact">
6937 Be able to emulate a DEC VT100 terminal, or a
6938 compatible terminal.
6942 Support the command-line option <tt>-e
6943 <var>command</var></tt>, which creates a new
6944 terminal window<footnote>
6946 "New terminal window" does not necessarily mean
6947 a new top-level X window directly parented by
6948 the window manager; it could, if the terminal
6949 emulator application were so coded, be a new
6950 "view" in a multiple-document interface (MDI).
6953 and runs the specified <var>command</var>.
6957 Support the command-line option <tt>-T
6958 <var>title</var></tt>, which creates a new terminal
6959 window with the window title <var>title</var>.
6966 <heading>Packages providing a window manager</heading>
6969 Packages that provide a window manager should declare in
6970 their control data that they provide the virtual package
6971 <tt>x-window-manager</tt>. They should also register
6972 themselves as an alternative for
6973 <file>/usr/bin/x-window-manager</file>, with a priority
6974 calculated as follows:
6975 <list compact="compact">
6976 <item><p>Start with a priority of 20.</p></item>
6980 If the window manager supports the Debian menu
6981 system, add 20 points if this support is available
6982 in the package's default configuration (i.e., no
6983 configuration files belonging to the system or user
6984 have to be edited to activate the feature); if
6985 configuration files must be modified, add only 10
6991 If the window manager complies with <url
6992 id="http://www.freedesktop.org/standards/wm-spec.html"
6993 name="The Window Manager Specification Project">,
6994 written by the <url id="http://www.freedesktop.org"
6995 name="Free Desktop Group">, add 20 points.
7001 If the window manager permits the X session to be
7002 restarted using a <em>different</em> window manager
7003 (without killing the X server) in its default
7004 configuration, add 10 points; otherwise add none.
7012 <heading>Packages providing fonts</heading>
7015 Packages that provide fonts for the X Window
7018 For the purposes of Debian Policy, a "font for the X
7019 Window System" is one which is accessed via X protocol
7020 requests. Fonts for the Linux console, for PostScript
7021 renderers, or any other purpose, do not fit this
7022 definition. Any tool which makes such fonts available
7023 to the X Window System, however, must abide by this
7027 must do a number of things to ensure that they are both
7028 available without modification of the X or font server
7029 configuration, and that they do not corrupt files used by
7030 other font packages to register information about
7035 Fonts of any type supported by the X Window System
7036 must be in a separate binary package from any
7037 executables, libraries, or documentation (except
7038 that specific to the fonts shipped, such as their
7039 license information). If one or more of the fonts
7040 so packaged are necessary for proper operation of
7041 the package with which they are associated the font
7042 package may be Recommended; if the fonts merely
7043 provide an enhancement, a Suggests relationship may
7044 be used. Packages must not Depend on font
7047 This is because the X server may retrieve fonts
7048 from the local filesystem or over the network
7049 from an X font server; the Debian package system
7050 is empowered to deal only with the local
7059 BDF fonts must be converted to PCF fonts with the
7060 <prgn>bdftopcf</prgn> utility (available in the
7061 <tt>xutils</tt> package, <tt>gzip</tt>ped, and
7062 placed in a directory that corresponds to their
7064 <list compact="compact">
7066 100 dpi fonts must be placed in
7067 <file>/usr/X11R6/lib/X11/fonts/100dpi/</file>.
7071 75 dpi fonts must be placed in
7072 <file>/usr/X11R6/lib/X11/fonts/75dpi/</file>.
7076 Character-cell fonts, cursor fonts, and other
7077 low-resolution fonts must be placed in
7078 <file>/usr/X11R6/lib/X11/fonts/misc/</file>.
7085 Speedo fonts must be placed in
7086 <file>/usr/X11R6/lib/X11/fonts/Speedo/</file>.
7090 Type 1 fonts must be placed in
7091 <file>/usr/X11R6/lib/X11/fonts/Type1/</file>. If font
7092 metric files are available, they must be placed here
7098 Subdirectories of <file>/usr/X11R6/lib/X11/fonts/</file>
7099 other than those listed above must be neither
7100 created nor used. (The <file>PEX</file>, <file>CID</file>,
7101 and <file>cyrillic</file> directories are excepted for
7102 historical reasons, but installation of files into
7103 these directories remains discouraged.)
7109 Font packages may, instead of placing files directly
7110 in the X font directories listed above, provide
7111 symbolic links in that font directory pointing to
7112 the files' actual location in the filesystem. Such
7113 a location must comply with the FHS.
7119 Font packages should not contain both 75dpi and
7120 100dpi versions of a font. If both are available,
7121 they should be provided in separate binary packages
7122 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
7123 the names of the packages containing the
7124 corresponding fonts.
7130 Fonts destined for the <file>misc</file> subdirectory
7131 should not be included in the same package as 75dpi
7132 or 100dpi fonts; instead, they should be provided in
7133 a separate package with <tt>-misc</tt> appended to
7140 Font packages must not provide the files
7141 <file>fonts.dir</file>, <file>fonts.alias</file>, or
7142 <file>fonts.scale</file> in a font directory:
7145 <file>fonts.dir</file> files must not be provided at all.
7150 <file>fonts.alias</file> and <file>fonts.scale</file>
7151 files, if needed, should be provided in the
7153 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
7154 where <var>fontdir</var> is the name of the
7156 <file>/usr/X11R6/lib/X11/fonts/</file> where the
7157 package's corresponding fonts are stored
7158 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
7159 <var>package</var> is the name of the package
7160 that provides these fonts, and
7161 <var>extension</var> is either <tt>scale</tt>
7162 or <tt>alias</tt>, whichever corresponds to
7172 Font packages must declare a dependency on
7173 <tt>xutils (>> 4.0.3)</tt> in their control
7180 Font packages that provide one or more
7181 <file>fonts.scale</file> files as described above must
7182 invoke <prgn>update-fonts-scale</prgn> on each
7183 directory into which they installed fonts
7184 <em>before</em> invoking
7185 <prgn>update-fonts-dir</prgn> on that directory.
7186 This invocation must occur in both the
7187 <prgn>postinst</prgn> (for all arguments) and
7188 <prgn>postrm</prgn> (for all arguments except
7189 <tt>upgrade</tt>) scripts.
7195 Font packages that provide one or more
7196 <file>fonts.alias</file> files as described above must
7197 invoke <prgn>update-fonts-alias</prgn> on each
7198 directory into which they installed fonts. This
7199 invocation must occur in both the
7200 <prgn>postinst</prgn> (for all arguments) and
7201 <prgn>postrm</prgn> (for all arguments except
7202 <tt>upgrade</tt>) scripts.
7208 Font packages must invoke
7209 <prgn>update-fonts-dir</prgn> on each directory into
7210 which they installed fonts. This invocation must
7211 occur in both the <prgn>postinst</prgn> (for all
7212 arguments) and <prgn>postrm</prgn> (for all
7213 arguments except <tt>upgrade</tt>) scripts.
7219 Font packages must not provide alias names for the
7220 fonts they include which collide with alias names
7221 already in use by fonts already packaged.
7227 Font packages must not provide fonts with the same
7228 XLFD registry name as another font already packaged.
7236 <heading>Application defaults files</heading>
7239 Application defaults files must be installed in the
7240 directory <file>/etc/X11/app-defaults/</file> (use of a
7241 localized subdirectory of <file>/etc/X11/</file> as described
7242 in the <em>X Toolkit Intrinsics - C Language
7243 Interface</em> manual is also permitted). They must be
7244 registered as <tt>conffile</tt>s or handled as
7245 configuration files. Packages must not provide the
7246 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
7250 Customization of programs' X resources may also be
7251 supported with the provision of a file with the same name
7252 as that of the package placed in the
7253 <file>/etc/X11/Xresources/</file> directory, which must
7254 registered as a <tt>conffile</tt> or handled as a
7255 configuration file.<footnote>
7257 Note that this mechanism is not the same as using
7258 app-defaults; app-defaults are tied to the client
7259 binary on the local filesystem, whereas X resources
7260 are stored in the X server and affect all connecting
7264 <em>Important:</em> packages that install files into the
7265 <file>/etc/X11/Xresources/</file> directory must conflict with
7266 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
7267 it is possible for the installing package to destroy a
7268 previously-existing <file>/etc/X11/Xresources</file> file
7269 which had been customized by the system administrator.
7274 <heading>Installation directory issues</heading>
7277 Packages using the X Window System should not be
7278 configured to install files under the <file>/usr/X11R6/</file>
7279 directory unless they use <prgn>imake</prgn>. The
7280 <file>/usr/X11R6/</file> directory hierarchy should be
7281 regarded as deprecated for all packages except the X
7282 Window System itself, and those which use the
7283 <prgn>imake</prgn> program it provides, in which case the
7284 packages may transition out of the <file>/usr/X11R6/</file>
7285 directory at the maintainer's discretion.<footnote>
7287 <prgn>Imake</prgn>-using programs are exempt because,
7288 as long as they are written correctly, the pathnames
7289 they use to locate resources and install themselves
7290 are derived wholly from the X Window System
7291 configuration. Thus, in the event that the X Window
7292 System moves to <file>/usr/X11R7/</file>,
7293 <file>/usr/X12/</file>, or just plain <file>/usr/</file>, all
7294 that is required for these programs is a recompile
7295 against the corresponding X Window System library
7296 development packages.
7299 Programs that use GNU <prgn>autoconf</prgn> and
7300 <prgn>automake</prgn> are usually easily configured at
7301 compile time to use <file>/usr/</file> instead of
7302 <file>/usr/X11R6/</file>, and this should be done whenever
7303 possible. Configuration files for window managers and
7304 display managers should be placed in a subdirectory of
7305 <file>/etc/X11/</file> corresponding to the package name due
7306 to these programs' tight integration with the mechanisms
7307 of the X Window System. Application-level programs should
7308 use the <file>/etc/</file> directory unless otherwise mandated
7309 by policy. The installation of files into subdirectories
7310 of <file>/usr/X11R6/include/X11/</file> and
7311 <file>/usr/X11R6/lib/X11/</file> is permitted but discouraged;
7312 package maintainers should determine if subdirectories of
7313 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
7314 instead. (The use of symbolic links from the
7315 <file>X11R6</file> directories to other FHS-compliant
7316 locations is encouraged if the program is not easily
7317 configured to look elsewhere for its files.) Packages
7318 must not provide or install files into the directories
7319 <file>/usr/bin/X11/</file>, <file>/usr/include/X11/</file> or
7320 <file>/usr/lib/X11/</file>. Files within a package should,
7321 however, make reference to these directories, rather than
7322 their <tt>X11R6</tt>-named counterparts
7323 <file>/usr/X11R6/bin/</file>, <file>/usr/X11R6/include/X11/</file>
7324 and <file>/usr/X11R6/lib/X11/</file>, if the resources being
7325 referred to have not been moved to other FHS-compliant
7331 <heading>The OSF/Motif and OpenMotif libraries</heading>
7334 <em>Programs that require the non-DFSG-compliant OSF/Motif or
7335 OpenMotif libraries</em><footnote>
7337 OSF/Motif and OpenMotif are collectively referred to as
7338 "Motif" in this policy document.
7341 should be compiled against and tested with LessTif (a free
7342 re-implementation of Motif) instead. If the maintainer
7343 judges that the program or programs do not work
7344 sufficiently well with LessTif to be distributed and
7345 supported, but do so when compiled against Motif, then two
7346 versions of the package should be created; one linked
7347 statically against Motif and with <tt>-smotif</tt>
7348 appended to the package name, and one linked dynamically
7349 against Motif and with <tt>-dmotif</tt> appended to the
7350 package name. Both Motif-linked versions are dependent
7351 upon non-DFSG-compliant software and thus cannot be
7352 uploaded to the <em>main</em> distribution; if the
7353 software is itself DFSG-compliant it may be uploaded to
7354 the <em>contrib</em> distribution. While known existing
7355 versions of Motif permit unlimited redistribution of
7356 binaries linked against the library (whether statically or
7357 dynamically), it is the package maintainer's
7358 responsibility to determine whether this is permitted by
7359 the license of the copy of Motif in his or her possession.
7365 <heading>Perl programs and modules</heading>
7367 Perl programs and modules should follow the current Perl
7368 policy as defined in the file found on
7369 <ftpsite>ftp.debian.org</ftpsite> in
7370 <ftppath>/debian/doc/package-developer/perl-policy.txt.gz</ftppath>
7371 or your local mirror. In addition, it is included in the
7372 <tt>debian-policy</tt> package.
7377 <heading>Emacs lisp programs</heading>
7380 Please refer to the `Debian Emacs Policy' (documented in
7381 <file>debian-emacs-policy.gz</file> of the
7382 <prgn>emacsen-common</prgn> package) for details of how to
7383 package emacs lisp programs.
7388 <heading>Games</heading>
7391 The permissions on <file>/var/games</file> are mode 755, owner
7392 <tt>root</tt> and group <tt>root</tt>.
7396 Each game decides on its own security policy.</p>
7399 Games which require protected, privileged access to
7400 high-score files, savegames, etc., may be made
7401 set-<em>group</em>-id (mode 2755) and owned by
7402 <tt>root.games</tt>, and use files and directories with
7403 appropriate permissions (770 <tt>root.games</tt>, for
7404 example). They must not be made
7405 set-<em>user</em>-id, as this causes security problems. (If
7406 an attacker can subvert any set-user-id game they can
7407 overwrite the executable of any other, causing other players
7408 of these games to run a Trojan horse program. With a
7409 set-group-id game the attacker only gets access to less
7410 important game data, and if they can get at the other
7411 players' accounts at all it will take considerably more
7415 Some packages, for example some fortune cookie programs, are
7416 configured by the upstream authors to install with their
7417 data files or other static information made unreadable so
7418 that they can only be accessed through set-id programs
7419 provided. You should not do this in a Debian package: anyone can
7420 download the <file>.deb</file> file and read the data from it,
7421 so there is no point making the files unreadable. Not
7422 making the files unreadable also means that you don't have
7423 to make so many programs set-id, which reduces the risk of a
7427 As described in the FHS, binaries of games should be
7428 installed in the directory <file>/usr/games</file>. This also
7429 applies to games that use the X Window System. Manual pages
7430 for games (X and non-X games) should be installed in
7431 <file>/usr/share/man/man6</file>.</p>
7435 <chapt id="docs"><heading>Documentation</heading>
7439 <heading>Manual pages</heading>
7442 You should install manual pages in <prgn>nroff</prgn> source
7443 form, in appropriate places under <file>/usr/share/man</file>. You
7444 should only use sections 1 to 9 (see the FHS for more
7445 details). You must not install a preformatted `cat
7449 Each program, utility, and function should have an
7450 associated manpage included in the same package. It is
7451 suggested that all configuration files also have a manual
7452 page included as well.
7456 There should be a manual page at for every program at the
7457 very least, and possibly one for every configuration file,
7458 protocol, utility, and function. If no manual page is
7459 available, this is considered as a bug and should be
7460 reported to the Debian Bug Tracking System (the maintainer
7461 of the package is allowed to write this bug report
7462 themselves, if they so desire). Do not close the bug report
7463 until a proper manpage is available.<footnote>
7465 It is not very hard to write a man page. See the
7466 <url id="http://www.schweikhardt.net/man_page_howto.html"
7467 name="Man-Page-HOWTO">,
7468 <manref name="man" section="7">, the examples
7469 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
7470 the helper programs <prgn>help2man</prgn>, or the
7471 directory <file>/usr/share/doc/man-db/examples</file>.
7477 You may forward a complaint about a missing manpage to the
7478 upstream authors, and mark the bug as forwarded in the
7479 Debian bug tracking system. Even though the GNU Project do
7480 not in general consider the lack of a manpage to be a bug,
7481 we do; if they tell you that they don't consider it a bug
7482 you should leave the bug in our bug tracking system open
7486 Manual pages should be installed compressed using <prgn>gzip</prgn>
7490 If one manpage needs to be accessible via several names it
7491 is better to use a symbolic link than the <file>.so</file>
7492 feature, but there is no need to fiddle with the relevant
7493 parts of the upstream source to change from <file>.so</file> to
7494 symlinks: don't do it unless it's easy. You should not
7495 create hard links in the manual page directories, nor put
7496 absolute filenames in <file>.so</file> directives. The filename
7497 in a <file>.so</file> in a manpage should be relative to the
7498 base of the manpage tree (usually
7499 <file>/usr/share/man</file>). If you do not create any links
7500 (whether symlinks, hard links, or <tt>.so</tt> directives)
7501 in the filesystem to the alternate names of the manpage,
7502 then you should not rely on <prgn>man</prgn> finding your
7503 manpage under those names based solely on the information in
7504 the manpage's header.<footnote>
7506 Supporting this in <prgn>man</prgn> often requires
7507 unreasonable processing time to find a manual page or to
7508 report that none exists, and moves knowledge into man's
7509 database that would be better left in the filesystem.
7510 This support is therefore deprecated and will cease to
7511 be present in the future.
7518 <heading>Info documents</heading>
7521 Info documents should be installed in <file>/usr/share/info</file>.
7522 They should be compressed with <tt>gzip -9</tt>.</p>
7525 Your package should call <prgn>install-info</prgn> to update
7526 the Info <file>dir</file> file in its <prgn>postinst</prgn>
7527 script when called with a <tt>configure</tt> argument, for
7529 <example compact="compact">
7530 install-info --quiet --section Development Development \
7531 /usr/share/info/foobar.info
7535 It is a good idea to specify a section for the location of
7536 your program; this is done with the <tt>--section</tt>
7537 switch. To determine which section to use, you should look
7538 at <file>/usr/share/info/dir</file> on your system and choose the most
7539 relevant (or create a new section if none of the current
7540 sections are relevant). Note that the <tt>--section</tt>
7541 flag takes two arguments; the first is a regular expression
7542 to match (case-insensitively) against an existing section,
7543 the second is used when creating a new one.</p>
7546 You should remove the entries in the <prgn>prerm</prgn>
7547 script when called with a <tt>remove</tt> argument:
7548 <example compact="compact">
7549 install-info --quiet --remove /usr/share/info/foobar.info
7553 If <prgn>install-info</prgn> cannot find a description entry
7554 in the Info file you must supply one. See <manref
7555 name="install-info" section="8"> for details.</p>
7559 <heading>Additional documentation</heading>
7562 Any additional documentation that comes with the package may
7563 be installed at the discretion of the package maintainer.
7564 Text documentation should be installed in the directory
7565 <file>/usr/share/doc/<var>package</var></file>, where
7566 <var>package</var> is the name of the package, and
7567 compressed with <tt>gzip -9</tt> unless it is small.</p>
7570 If a package comes with large amounts of documentation which
7571 many users of the package will not require you should create
7572 a separate binary package to contain it, so that it does not
7573 take up disk space on the machines of users who do not need
7574 or want it installed.</p>
7577 It is often a good idea to put text information files
7578 (<file>README</file>s, changelogs, and so forth) that come with
7579 the source package in <file>/usr/share/doc/<var>package</var></file>
7580 in the binary package. However, you don't need to install
7581 the instructions for building and installing the package, of
7585 Packages must not require the existance of any files in
7586 <file>/usr/share/doc/</file> in order to function
7587 <footnote id="rationale">
7589 The system administrator should be able to
7590 delete files in <file>/usr/share/doc/</file> without causing
7591 any programs to break.
7594 Any files that are referenced by programs but are also
7595 useful as standalone documentation should be installed under
7596 <file>/usr/share/doc/</file> with symbolic links from
7597 <file>/usr/share/doc/<package></file>
7601 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7602 link to another directory in <file>/usr/share/doc</file> only if
7603 the two packages both come from the same source and the
7604 first package Depends on the second.
7608 Former Debian releases placed all additional documentation
7609 in <file>/usr/doc/<var>package</var></file>. This has been
7610 changed to <file>/usr/share/doc/<var>package</var></file>,
7611 and packages must not put documentation in the directory
7612 <file>/usr/doc/<var>package</var></file>. <footnote>
7613 <p>At this phase of the transition, we no longer require a
7614 symbolic link in <file>/usr/doc/</file>. At a later point,
7615 policy shall change to make the symbolic links a bug.</p>
7621 <heading>Preferred documentation formats</heading>
7624 The unification of Debian documentation is being carried out
7628 If your package comes with extensive documentation in a
7629 markup format that can be converted to various other formats
7630 you should if possible ship HTML versions in a binary
7631 package, in the directory
7632 <file>/usr/share/doc/<var>appropriate-package</var></file> or
7633 its subdirectories.<footnote>
7635 The rationale: The important thing here is that HTML
7636 docs should be available in <em>some</em> package, not
7637 necessarily in the main binary package.
7643 Other formats such as PostScript may be provided at the
7644 package maintainer's discretion.
7648 <sect id="copyrightfile">
7649 <heading>Copyright information</heading>
7652 Every package must be accompanied by a verbatim copy of its
7653 copyright and distribution license in the file
7654 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
7655 file must neither be compressed nor be a symbolic link.
7659 In addition, the copyright file must say where the upstream
7660 sources (if any) were obtained. It should name the original
7661 authors of the package and the Debian maintainer(s) who were
7662 involved with its creation.</p>
7665 A copy of the file which will be installed in
7666 <file>/usr/share/doc/<var>package</var>/copyright</file> should
7667 be in <file>debian/copyright</file> in the source package.
7671 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7672 link to another directory in <file>/usr/share/doc</file> only if
7673 the two packages both come from the same source and the
7674 first package Depends on the second. These rules are
7675 important because copyrights must be extractable by
7680 Packages distributed under the UCB BSD license, the Artistic
7681 license, the GNU GPL, and the GNU LGPL should refer to the
7682 files <file>/usr/share/common-licenses/BSD</file>,
7683 <file>/usr/share/common-licenses/Artistic</file>,
7684 <file>/usr/share/common-licenses/GPL</file>, and
7685 <file>/usr/share/common-licenses/LGPL</file> respectively,
7686 rather than quoting them in the copyright file.
7690 You should not use the copyright file as a general <file>README</file>
7691 file. If your package has such a file it should be
7692 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
7693 <file>README.Debian</file> or some other appropriate place.</p>
7697 <heading>Examples</heading>
7700 Any examples (configurations, source files, whatever),
7701 should be installed in a directory
7702 <file>/usr/share/doc/<var>package</var>/examples</file>. These
7703 files should not be referenced by any program: they're there
7704 for the benefit of the system administrator and users as
7705 documentation only. Architecture-specific example files
7706 should be installed in a directory
7707 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
7709 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
7710 latter directory itself may be a symbolic link to the
7715 <sect id="changelogs">
7716 <heading>Changelog files</heading>
7719 The Debian changelog file (<file>debian/changelog</file>) should
7720 explain briefly what modifications were made in the Debian version
7721 of the package compared to the upstream one. Other changes and
7722 updates to the package should also be documented in this file.
7726 Mistakes in changelogs are usually best rectified by
7727 making a new changelog entry rather than "rewriting history"
7728 by editing old changelog entries.
7732 The format of the <file>debian/changelog</file> file is described
7733 in <ref id="dpkgchangelog">. In non-experimental packages you must
7734 use a format for <file>debian/changelog</file> which is supported
7735 by the most recent released version of <prgn>dpkg</prgn>.<footnote>
7737 If you wish to use an alternative format, you may do so as long
7738 as you include a parser for it in your source package. The
7739 parser must have an API compatible with that expected by
7740 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-gencontrol</prgn>.
7741 If there is general interest in the new format, you should
7742 contact the <package>dpkg</package> maintainer to have the
7743 parser script for it included in the <prgn>dpkg</prgn> package.
7744 (You will need to agree that the parser and its manpage may be
7745 distributed under the GNU GPL, just as the rest of `dpkg' is.)
7751 Packages that are not Debian-native must contain a
7752 compressed copy of the <file>debian/changelog</file> file from
7753 the Debian source tree in
7754 <file>/usr/share/doc/<var>package</var></file> with the name
7755 <file>changelog.Debian.gz</file>.
7759 If an upstream changelog is available, it should be accessible as
7760 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
7761 plain text. If the upstream changelog is distributed in
7762 HTML, it should be made available in that form as
7763 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
7764 and a plain text <file>changelog.gz</file> should be generated
7765 from it using, for example, <tt>lynx -dump -nolist</tt>. If
7766 the upstream changelog files do not already conform to this
7767 naming convention, then this may be achieved either by
7768 renaming the files, or by adding a symbolic link, at the
7769 maintainer's discretion.<footnote>
7771 Rationale: People should not have to look in places for
7772 upstream changelogs merely because they are given
7773 different names or are distributed in HTML format.
7779 All of these files should be installed compressed using
7780 <tt>gzip -9</tt>, as they will become large with time even
7781 if they start out small.
7785 If the package has only one changelog which is used both as
7786 the Debian changelog and the upstream one because there is
7787 no separate upstream maintainer then that changelog should
7788 usually be installed as
7789 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
7790 there is a separate upstream maintainer, but no upstream
7791 changelog, then the Debian changelog should still be called
7792 <file>changelog.Debian.gz</file>.</p>
7797 <appendix id="pkg-scope">
7798 <heading>Introduction and scope of these appendices</heading>
7801 These appendices are taken essentially verbatim from the
7802 now-deprecated Packaging Manual, version 3.2.1.0. They are
7803 the chapters which are likely to be of use to package
7804 maintainers and which have not already been included in the
7805 policy document itself. Most of these sections are very likely
7806 not relevant to policy; they should be treated as
7807 documentation for the packaging system. Please note that these
7808 appendices are included for convenience, and for historical
7809 reasons: they used to be part of policy package, and they have
7810 not yet been incorporated into dpkg documentation. However,
7811 they still have value, and hence they are presented here.
7814 They have not yet been checked to ensure that they are
7815 compatible with the contents of policy, and if there are any
7816 contradictions, the version in the main policy document takes
7817 precedence. The remaining chapters of the old Packaging
7818 Manual have also not been read in detail to ensure that there
7819 are not parts which have been left out. Both of these will be
7824 <prgn>dpkg</prgn> is a suite of programs for creating binary
7825 package files and installing and removing them on Unix
7828 <prgn>dpkg</prgn> is targetted primarily at Debian
7829 GNU/Linux, but may work on or be ported to other
7836 The binary packages are designed for the management of
7837 installed executable programs (usually compiled binaries) and
7838 their associated data, though source code examples and
7839 documentation are provided as part of some packages.</p>
7842 This manual describes the technical aspects of creating Debian
7843 binary packages (<file>.deb</file> files). It documents the
7844 behaviour of the package management programs
7845 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
7846 they interact with packages.</p>
7849 It also documents the interaction between
7850 <prgn>dselect</prgn>'s core and the access method scripts it
7851 uses to actually install the selected packages, and describes
7852 how to create a new access method.</p>
7855 This manual does not go into detail about the options and
7856 usage of the package building and installation tools. It
7857 should therefore be read in conjuction with those programs'
7862 The utility programs which are provided with <prgn>dpkg</prgn>
7863 for managing various system configuration and similar issues,
7864 such as <prgn>update-rc.d</prgn> and
7865 <prgn>install-info</prgn>, are not described in detail here -
7866 please see their manpages.
7870 It does <em>not</em> describe the policy requirements imposed
7871 on Debian packages, such as the permissions on files and
7872 directories, documentation requirements, upload procedure, and
7873 so on. You should see the Debian packaging policy manual for
7874 these details. (Many of them will probably turn out to be
7875 helpful even if you don't plan to upload your package and make
7876 it available as part of the distribution.)
7880 It is assumed that the reader is reasonably familiar with the
7881 <prgn>dpkg</prgn> System Administrators' manual.
7882 Unfortunately this manual does not yet exist.
7886 The Debian version of the FSF's GNU hello program is provided
7887 as an example for people wishing to create Debian
7888 packages. The Debian <prgn>debmake</prgn> package is
7889 recommended as a very helpful tool in creating and maintaining
7890 Debian packages. However, while the tools and examples are
7891 helpful, they do not replace the need to read and follow the
7892 Policy and Programmer's Manual.</p>
7895 <appendix id="pkg-binarypkg"><heading>Binary packages (from old
7900 The binary package has two main sections. The first part
7901 consists of various control information files and scripts used
7902 by <prgn>dpkg</prgn> when installing and removing. See <ref
7903 id="pkg-controlarea">.
7907 The second part is an archive containing the files and
7908 directories to be installed.
7912 In the future binary packages may also contain other
7913 components, such as checksums and digital signatures. The
7914 format for the archive is described in full in the
7915 <file>deb(5)</file> manpage.
7919 <sect id="pkg-bincreating"><heading>Creating package files -
7920 <prgn>dpkg-deb</prgn>
7924 All manipulation of binary package files is done by
7925 <prgn>dpkg-deb</prgn>; it's the only program that has
7926 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
7927 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
7928 will spot that the options requested are appropriate to
7929 <prgn>dpkg-deb</prgn> and invoke that instead with the same
7934 In order to create a binary package you must make a
7935 directory tree which contains all the files and directories
7936 you want to have in the filesystem data part of the package.
7937 In Debian-format source packages this directory is usually
7938 <file>debian/tmp</file>, relative to the top of the package's
7943 They should have the locations (relative to the root of the
7944 directory tree you're constructing) ownerships and
7945 permissions which you want them to have on the system when
7950 With current versions of <prgn>dpkg</prgn> the uid/username
7951 and gid/groupname mappings for the users and groups being
7952 used should be the same on the system where the package is
7953 built and the one where it is installed.
7957 You need to add one special directory to the root of the
7958 miniature filesystem tree you're creating:
7959 <prgn>DEBIAN</prgn>. It should contain the control
7960 information files, notably the binary package control file
7961 (see <ref id="pkg-controlfile">).
7965 The <prgn>DEBIAN</prgn> directory will not appear in the
7966 filesystem archive of the package, and so won't be installed
7967 by <prgn>dpkg</prgn> when the package is installed.
7971 When you've prepared the package, you should invoke:
7973 dpkg --build <var>directory</var>
7978 This will build the package in
7979 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
7980 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
7981 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
7986 See the manpage <manref name="dpkg-deb" section="8"> for details of how
7987 to examine the contents of this newly-created file. You may find the
7988 output of following commands enlightening:
7990 dpkg-deb --info <var>filename</var>.deb
7991 dpkg-deb --contents <var>filename</var>.deb
7992 dpkg --contents <var>filename</var>.deb
7994 To view the copyright file for a package you could use this command:
7996 dpkg --fsys-tarfile <var>filename</var>.deb | tar xof usr/share/doc/<var>\*</var>copyright | less
8001 <sect id="pkg-controlarea">
8003 Package control information files
8007 The control information portion of a binary package is a
8008 collection of files with names known to <prgn>dpkg</prgn>.
8009 It will treat the contents of these files specially - some
8010 of them contain information used by <prgn>dpkg</prgn> when
8011 installing or removing the package; others are scripts which
8012 the package maintainer wants <prgn>dpkg</prgn> to run.
8016 It is possible to put other files in the package control
8017 area, but this is not generally a good idea (though they
8018 will largely be ignored).
8022 Here is a brief list of the control info files supported by
8023 <prgn>dpkg</prgn> and a summary of what they're used for.
8028 <tag><tt>control</tt>
8032 This is the key description file used by
8033 <prgn>dpkg</prgn>. It specifies the package's name
8034 and version, gives its description for the user,
8035 states its relationships with other packages, and so
8036 forth. See <ref id="pkg-controlfile">.
8040 It is usually generated automatically from information
8041 in the source package by the
8042 <prgn>dpkg-gencontrol</prgn> program, and with
8043 assistance from <prgn>dpkg-shlibdeps</prgn>. See <ref
8044 id="pkg-sourcetools">.</p>
8047 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
8053 These are exectuable files (usually scripts) which
8054 <prgn>dpkg</prgn> runs during installation, upgrade
8055 and removal of packages. They allow the package to
8056 deal with matters which are particular to that package
8057 or require more complicated processing than that
8058 provided by <prgn>dpkg</prgn>. Details of when and
8059 how they are called are in <ref
8060 id="maintainerscripts">.
8064 It is very important to make these scripts
8068 That means that if it runs successfully or fails
8069 and then you call it again it doesn't bomb out,
8070 but just ensures that everything is the way it
8073 </footnote> This is so that if an error occurs, the
8074 user interrupts <prgn>dpkg</prgn> or some other
8075 unforeseen circumstance happens you don't leave the
8076 user with a badly-broken package.
8080 The maintainer scripts are guaranteed to run with a
8081 controlling terminal and can interact with the user.
8082 If they need to prompt for passwords, do full-screen
8083 interaction or something similar you should do these
8084 things to and from <file>/dev/tty</file>, since
8085 <prgn>dpkg</prgn> will at some point redirect scripts'
8086 standard input and output so that it can log the
8087 installation process. Likewise, because these scripts
8088 may be executed with standard output redirected into a
8089 pipe for logging purposes, Perl scripts should set
8090 unbuffered output by setting <tt>$|=1</tt> so that the
8091 output is printed immediately rather than being
8096 Each script should return a zero exit status for
8097 success, or a nonzero one for failure.</p>
8100 <tag><tt>conffiles</tt>
8105 This file contains a list of configuration files which
8106 are to be handled automatically by <prgn>dpkg</prgn>
8107 (see <ref id="pkg-conffiles">). Note that not necessarily
8108 every configuration file should be listed here.</p>
8111 <tag><tt>shlibs</tt>
8116 This file contains a list of the shared libraries
8117 supplied by the package, with dependency details for
8118 each. This is used by <prgn>dpkg-shlibdeps</prgn>
8119 when it determines what dependencies are required in a
8120 package control file. The <tt>shlibs</tt> file format
8121 is described on <ref id="shlibs">.
8127 <sect id="pkg-controlfile">
8129 The main control information file: <tt>control</tt>
8132 The most important control information file used by
8133 <prgn>dpkg</prgn> when it installs a package is
8134 <tt>control</tt>. It contains all the package's `vital
8139 The binary package control files of packages built from
8140 Debian sources are made by a special tool,
8141 <prgn>dpkg-gencontrol</prgn>, which reads
8142 <file>debian/control</file> and <file>debian/changelog</file> to
8143 find the information it needs. See <ref id="pkg-sourcepkg"> for
8148 The fields in binary package control files are:
8149 <list compact="compact">
8151 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8154 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
8156 <item><p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8160 This field should appear in all packages, though
8161 <prgn>dpkg</prgn> doesn't require it yet so that
8162 old packages can still be installed.
8168 <p><qref id="relationships"><tt>Depends</tt>,
8169 <tt>Provides</tt> et al.</qref></p>
8172 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8175 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8178 <p><qref id="pkg-f-classification"><tt>Section</tt>,
8179 <tt>Priority</tt></qref></p>
8182 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
8185 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8189 <qref id="pkg-f-Installed-Size"><tt>Installed-Size</tt></qref>
8195 A description of the syntax of control files and the purpose
8196 of these fields is available in <ref id="pkg-controlfields">.
8201 <heading>Time Stamps</heading>
8203 Maintainers are encouraged to preserve the modification
8204 times of the upstream source files in a package, as far as
8205 is reasonably possible.
8208 The rationale is that there is some information conveyed
8209 by knowing the age of the file, for example, you could
8210 recognize that some documentation is very old by looking
8211 at the modification time, so it would be nice if the
8212 modification time of the upstream source would be
8220 <appendix id="pkg-sourcepkg">
8221 <heading>Source packages (from old Packaging Manual) </heading>
8224 The Debian binary packages in the distribution are generated
8225 from Debian sources, which are in a special format to assist
8226 the easy and automatic building of binaries.
8230 There was a previous version of the Debian source format,
8231 which is now being phased out. Instructions for converting an
8232 old-style package are given in the Debian policy manual.
8235 <sect id="pkg-sourcetools">
8236 <heading>Tools for processing source packages</heading>
8239 Various tools are provided for manipulating source packages;
8240 they pack and unpack sources and help build of binary
8241 packages and help manage the distribution of new versions.
8245 They are introduced and typical uses described here; see
8246 <manref name="dpkg-source" section="1"> for full
8247 documentation about their arguments and operation.
8251 For examples of how to construct a Debian source package,
8252 and how to use those utilities that are used by Debian
8253 source packages, please see the <prgn>hello</prgn> example
8259 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
8264 This program is frequently used by hand, and is also
8265 called from package-independent automated building scripts
8266 such as <prgn>dpkg-buildpackage</prgn>.
8270 To unpack a package it is typically invoked with
8272 dpkg-source -x <var>.../path/to/filename</var>.dsc
8277 with the <file><var>filename</var>.tar.gz</file> and
8278 <file><var>filename</var>.diff.gz</file> (if applicable) in
8279 the same directory. It unpacks into
8280 <file><var>package</var>-<var>version</var></file>, and if
8282 <file><var>package</var>-<var>version</var>.orig</file>, in
8283 the current directory.
8287 To create a packed source archive it is typically invoked:
8289 dpkg-source -b <var>package</var>-<var>version</var>
8294 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
8295 <file>.diff.gz</file> (if appropriate) in the current
8296 directory. <prgn>dpkg-source</prgn> does not clean the
8297 source tree first - this must be done separately if it is
8302 See also <ref id="pkg-sourcearchives">.</p>
8308 <prgn>dpkg-buildpackage</prgn> - overall package-building
8313 <prgn>dpkg-buildpackage</prgn> is a script which invokes
8314 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
8315 targets <tt>clean</tt>, <tt>build</tt> and
8316 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
8317 <prgn>pgp</prgn> to build a signed source and binary
8322 It is usually invoked by hand from the top level of the
8323 built or unbuilt source directory. It may be invoked with
8324 no arguments; useful arguments include:
8325 <taglist compact="compact">
8326 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
8329 Do not PGP-sign the <tt>.changes</tt> file or the
8330 source package <tt>.dsc</tt> file, respectively.</p>
8332 <tag><tt>-p<var>pgp-command</var></tt></tag>
8335 Invoke <var>pgp-command</var> instead of finding
8336 <tt>pgp</tt> on the <prgn>PATH</prgn>.
8337 <var>pgp-command</var> must behave just like
8338 <prgn>pgp</prgn>.</p>
8340 <tag><tt>-r<var>root-command</var></tt></tag>
8343 When root privilege is required, invoke the command
8344 <var>root-command</var>. <var>root-command</var>
8345 should invoke its first argument as a command, from
8346 the <prgn>PATH</prgn> if necessary, and pass its
8347 second and subsequent arguments to the command it
8348 calls. If no <var>root-command</var> is supplied
8349 then <var>dpkg-buildpackage</var> will take no
8350 special action to gain root privilege, so that for
8351 most packages it will have to be invoked as root to
8354 <tag><tt>-b</tt>, <tt>-B</tt></tag>
8357 Two types of binary-only build and upload - see
8358 <manref name="dpkg-source" section="1">.
8367 <prgn>dpkg-gencontrol</prgn> - generates binary package
8372 This program is usually called from <file>debian/rules</file>
8373 (see <ref id="pkg-sourcetree">) in the top level of the source
8378 This is usually done just before the files and directories in the
8379 temporary directory tree where the package is being built have their
8380 permissions and ownerships set and the package is constructed using
8381 <prgn>dpkg-deb/</prgn>
8384 This is so that the control file which is produced has
8385 the right permissions
8391 <prgn>dpkg-gencontrol</prgn> must be called after all the
8392 files which are to go into the package have been placed in
8393 the temporary build directory, so that its calculation of
8394 the installed size of a package is correct.
8398 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
8399 be run after <prgn>dpkg-shlibdeps</prgn> so that the
8400 variable substitutions created by
8401 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
8406 For a package which generates only one binary package, and
8407 which builds it in <file>debian/tmp</file> relative to the top
8408 of the source package, it is usually sufficient to call
8409 <prgn>dpkg-gencontrol</prgn>.
8413 Sources which build several binaries will typically need
8416 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
8417 </example> The <tt>-P</tt> tells
8418 <prgn>dpkg-gencontrol</prgn> that the package is being
8419 built in a non-default directory, and the <tt>-p</tt>
8420 tells it which package's control file should be generated.
8424 <prgn>dpkg-gencontrol</prgn> also adds information to the
8425 list of files in <file>debian/files</file>, for the benefit of
8426 (for example) a future invocation of
8427 <prgn>dpkg-genchanges</prgn>.</p>
8432 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
8437 This program is usually called from <file>debian/rules</file>
8438 just before <prgn>dpkg-gencontrol</prgn> (see <ref
8439 id="pkg-sourcetree">), in the top level of the source tree.
8443 Its arguments are executables.
8446 In a forthcoming dpkg version,
8447 <prgn>dpkg-shlibdeps</prgn> would be required to be
8448 called on shared libraries as well.
8451 They may be specified either in the locations in the
8452 source tree where they are created or in the locations
8453 in the temporary build tree where they are installed
8454 prior to binary package creation.
8456 </footnote> for which shared library dependencies should
8457 be included in the binary package's control file.
8461 If some of the found shared libraries should only
8462 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
8463 some warrant a <tt>Pre-Depends</tt>, this can be achieved
8464 by using the <tt>-d<var>dependency-field</var></tt> option
8465 before those executable(s). (Each <tt>-d</tt> option
8466 takes effect until the next <tt>-d</tt>.)
8470 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
8471 output control file to be modified. Instead by default it
8472 adds to the <file>debian/substvars</file> file variable
8473 settings like <tt>shlibs:Depends</tt>. These variable
8474 settings must be referenced in dependency fields in the
8475 appropriate per-binary-package sections of the source
8480 For example, the <prgn>procps</prgn> package generates two
8481 kinds of binaries, simple C binaries like <prgn>ps</prgn>
8482 which require a predependency and full-screen ncurses
8483 binaries like <prgn>top</prgn> which require only a
8484 recommendation. It can say in its <file>debian/rules</file>:
8486 dpkg-shlibdeps -dPre-Depends ps -dRecommends top
8488 and then in its main control file <file>debian/control</file>:
8492 Pre-Depends: ${shlibs:Pre-Depends}
8493 Recommends: ${shlibs:Recommends}
8499 Sources which produce several binary packages with
8500 different shared library dependency requirements can use
8501 the <tt>-p<var>varnameprefix</var></tt> option to override
8502 the default <tt>shlibs:</tt> prefix (one invocation of
8503 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
8504 They can thus produce several sets of dependency
8505 variables, each of the form
8506 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
8507 which can be referred to in the appropriate parts of the
8508 binary package control files.
8515 <prgn>dpkg-distaddfile</prgn> - adds a file to
8516 <file>debian/files</file>
8520 Some packages' uploads need to include files other than
8521 the source and binary package files.
8525 <prgn>dpkg-distaddfile</prgn> adds a file to the
8526 <file>debian/files</file> file so that it will be included in
8527 the <file>.changes</file> file when
8528 <prgn>dpkg-genchanges</prgn> is run.
8532 It is usually invoked from the <tt>binary</tt> target of
8533 <file>debian/rules</file>:
8535 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
8537 The <var>filename</var> is relative to the directory where
8538 <prgn>dpkg-genchanges</prgn> will expect to find it - this
8539 is usually the directory above the top level of the source
8540 tree. The <file>debian/rules</file> target should put the
8541 file there just before or just after calling
8542 <prgn>dpkg-distaddfile</prgn>.
8546 The <var>section</var> and <var>priority</var> are passed
8547 unchanged into the resulting <file>.changes</file> file. See
8548 <ref id="pkg-f-classification">.
8553 <sect1><heading><prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file> upload
8558 This program is usually called by package-independent
8559 automatic building scripts such as
8560 <prgn>dpkg-buildpackage</prgn>, but it may also be called
8565 It is usually called in the top level of a built source
8566 tree, and when invoked with no arguments will print out a
8567 straightforward <file>.changes</file> file based on the
8568 information in the source package's changelog and control
8569 file and the binary and source packages which should have
8575 <sect1><heading><prgn>dpkg-parsechangelog</prgn> - produces parsed representation of
8580 This program is used internally by
8581 <prgn>dpkg-source</prgn> et al. It may also occasionally
8582 be useful in <file>debian/rules</file> and elsewhere. It
8583 parses a changelog, <file>debian/changelog</file> by default,
8584 and prints a control-file format representation of the
8585 information in it to standard output.
8589 <sect1 id="pkg-dpkgarch"><heading><prgn>dpkg-architecture</prgn> -
8590 information about the build and host system
8594 This program can be used manually, but is also invoked by
8595 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
8596 to set environment or make variables which specify the build and
8597 host architecture for the package building process.
8602 <sect id="pkg-sourcetree"><heading>The Debianised source tree
8606 The source archive scheme described later is intended to
8607 allow a Debianised source tree with some associated control
8608 information to be reproduced and transported easily. The
8609 Debianised source tree is a version of the original program
8610 with certain files added for the benefit of the
8611 Debianisation process, and with any other changes required
8612 made to the rest of the source code and installation
8617 The extra files created for Debian are in the subdirectory
8618 <file>debian</file> of the top level of the Debianised source
8619 tree. They are described below.
8622 <sect1 id="pkg-debianrules"><heading><file>debian/rules</file> - the main building
8627 This file is an executable makefile, and contains the
8628 package-specific recipies for compiling the package and
8629 building binary package(s) out of the source.
8633 It must start with the line <tt>#!/usr/bin/make -f</tt>,
8634 so that it can be invoked by saying its name rather than
8635 invoking <prgn>make</prgn> explicitly.
8639 Since an interactive <file>debian/rules</file> script makes it
8640 impossible to autocompile that package and also makes it
8641 hard for other people to reproduce the same binary
8642 package, all <strong>required targets</strong> have to be
8643 non-interactive. At a minimul, required targets are the
8644 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
8645 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>, and
8646 <em>build</em>. It also follows that any target that these
8647 targets depend on must also be non-interactive.
8651 The targets which are required to be present are:
8653 <tag><tt>build</tt></tag>
8656 This should perform all non-interactive
8657 configuration and compilation of the package. If a
8658 package has an interactive pre-build configuration
8659 routine, the Debianised source package should be
8660 built after this has taken place, so that it can be
8661 built without rerunning the configuration.
8665 A package may also provide both of the targets
8666 <tt>build-arch</tt> and <tt>build-indep</tt>. The
8667 <tt>build-arch</tt> target, if provided, should
8668 perform all non-interactive configuration and
8669 compilation required for producing all
8670 architecture-dependant binary packages (those packages
8671 for which the body of the <tt>Architecture</tt> field
8672 in <tt>debian/control</tt> is not <tt>all</tt>).
8673 Similarly, the <tt>build-indep</tt> target, if
8674 provided, should perform all non-interactive
8675 configuration and compilation required for producing
8676 all architecture-independent binary packages (those
8677 packages for which the body of the
8678 <tt>Architecture</tt> field in <tt>debian/control</tt>
8679 is <tt>all</tt>). The <tt>build</tt> target should
8680 depend on those of the targets <tt>build-arch</tt> and
8681 <tt>build-indep</tt> that are provided in the rules
8686 If one or both of the targets <tt>build-arch</tt> and
8687 <tt>build-indep</tt> are not provided, then invoking
8688 <file>debian/rules</file> with one of the not-provided
8689 targets as arguments should produce a exit status code
8690 of 2. Usually this is provided automatically by make
8691 if the target is missing.
8695 For some packages, notably ones where the same
8696 source tree is compiled in different ways to produce
8697 two binary packages, the <tt>build</tt> target does
8698 not make much sense. For these packages it is good
8699 enough to provide two (or more) targets
8700 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
8701 for each of the ways of building the package, and a
8702 <tt>build</tt> target that does nothing. The
8703 <tt>binary</tt> target will have to build the
8704 package in each of the possible ways and make the
8705 binary package out of each.
8709 The targets <tt>build</tt>, <tt>build-arch</tt>
8710 and <tt>build-indep</tt> target must not do
8711 anything that might require root privilege.
8715 The <tt>build</tt> target may need to run
8716 <tt>clean</tt> first - see below.
8720 When a package has a configuration routine that takes
8721 a long time, or when the makefiles are poorly
8722 designed, or when <tt>build</tt> needs to run
8723 <tt>clean</tt> first, it is a good idea to <tt>touch
8724 build</tt> when the build process is complete. This
8725 will ensure that if <tt>debian/rules build</tt> is run
8726 again it will not rebuild the whole program.
8730 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
8731 <tt>binary-indep</tt>
8735 The <tt>binary</tt> target should be all that is
8736 necessary for the user to build the binary
8737 package. All these targets are required to be
8738 non-interactive. It is split into two parts:
8739 <tt>binary-arch</tt> builds the packages' output
8740 files which are specific to a particular
8741 architecture, and <tt>binary-indep</tt> builds
8742 those which are not.
8746 <tt>binary</tt> should usually be a target with
8747 no commands which simply depends on
8748 <prgn>binary-arch</prgn> and
8749 <prgn>binary-indep</prgn>.
8753 Both <prgn>binary-*</prgn> targets should depend on
8754 the <tt>build</tt> target, above, so that the
8755 package is built if it has not been already. It
8756 should then create the relevant binary package(s),
8757 using <prgn>dpkg-gencontrol</prgn> to make their
8758 control files and <prgn>dpkg-deb</prgn> to build
8759 them and place them in the parent of the top level
8764 If one of the <prgn>binary-*</prgn> targets has
8765 nothing to do (this will be always be the case if
8766 the source generates only a single binary package,
8767 whether architecture-dependent or not) it
8768 <em>must</em> still exist, but should always
8773 <ref id="pkg-binarypkg"> describes how to construct
8778 The <tt>binary</tt> targets must be invoked as
8783 <tag><tt>clean</tt></tag>
8787 This should undo any effects that the
8788 <tt>build</tt> and <tt>binary</tt> targets
8789 may have had, except that it should leave alone any
8790 output files created in the parent directory by a
8791 run of <tt>binary</tt>. This target is required
8792 to be non-interactive.
8796 If a <tt>build</tt> file is touched at the end
8797 of the <tt>build</tt> target, as suggested
8798 above, it must be removed as the first thing that
8799 <tt>clean</tt> does, so that running
8800 <tt>build</tt> again after an interrupted
8801 <tt>clean</tt> doesn't think that everything is
8806 The <tt>clean</tt> target must be invoked as
8807 root if <tt>binary</tt> has been invoked since
8808 the last <tt>clean</tt>, or if
8809 <tt>build</tt> has been invoked as root (since
8810 <tt>build</tt> may create directories, for
8815 <tag><tt>get-orig-source</tt> (optional)</tag>
8819 This target fetches the most recent version of the
8820 original source package from a canonical archive
8821 site (via FTP or WWW, for example), does any
8822 necessary rearrangement to turn it into the original
8823 source tarfile format described below, and leaves it
8824 in the current directory.
8828 This target may be invoked in any directory, and
8829 should take care to clean up any temporary files it
8834 This target is optional, but providing it if
8835 possible is a good idea.
8841 The <tt>build</tt>, <tt>binary</tt> and
8842 <tt>clean</tt> targets must be invoked with a current
8843 directory of the package's top-level directory.
8848 Additional targets may exist in <file>debian/rules</file>,
8849 either as published or undocumented interfaces or for the
8850 package's internal use.
8854 The architecture we build on and build for is determined by make
8855 variables via dpkg-architecture (see <ref id="pkg-dpkgarch">). You can
8856 get the Debian architecture and the GNU style architecture
8857 specification string for the build machine as well as the host
8858 machine. Here is a list of supported make variables:
8859 <list compact="compact">
8861 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
8864 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
8865 specification string)</p>
8868 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of DEB_*_GNU_TYPE)</p>
8871 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
8877 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
8878 the build machine or <tt>HOST</tt> for specification of the machine
8883 Backward compatibility can be provided in the rules file
8884 by setting the needed variables to suitable default
8885 values, please refer to the documentation of
8886 dpkg-architecture for details.
8890 It is important to understand that the <tt>DEB_*_ARCH</tt>
8891 string does only determine which Debian architecture we
8892 build on resp. for. It should not be used to get the CPU
8893 or System information, the GNU style variables should be
8899 <sect1><heading><file>debian/control</file>
8903 This file contains version-independent details about the
8904 source package and about the binary packages it creates.
8908 It is a series of sets of control fields, each
8909 syntactically similar to a binary package control file.
8910 The sets are separated by one or more blank lines. The
8911 first set is information about the source package in
8912 general; each subsequent set describes one binary package
8913 that the source tree builds.
8917 The syntax and semantics of the fields are described below
8918 in <ref id="pkg-controlfields">.
8922 The general (binary-package-independent) fields are:
8923 <list compact="compact">
8925 <p><qref id="pkg-f-Source"><tt>Source</tt></qref> (mandatory)</p>
8928 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8932 <qref id="pkg-f-classification"><tt>Section</tt> and
8933 <tt>Priority</tt></qref>
8934 (classification, mandatory)
8939 <qref id="relationships"><tt>Build-Depends</tt> et
8940 al.</qref> (source package interrelationships)
8945 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref>
8951 The per-binary-package fields are:
8952 <list compact="compact">
8954 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8958 <qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8962 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8966 <qref id="pkg-f-classification"><tt>Section</tt> and
8967 <tt>Priority</tt></qref> (classification)</p>
8970 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8974 <qref id="relationships"><tt>Depends</tt> et
8975 al.</qref> (binary package interrelationships)
8981 These fields are used by <prgn>dpkg-gencontrol</prgn> to
8982 generate control files for binary packages (see below), by
8983 <prgn>dpkg-genchanges</prgn> to generate the
8984 <tt>.changes</tt> file to accompany the upload, and by
8985 <prgn>dpkg-source</prgn> when it creates the <file>.dsc</file>
8986 source control file as part of a source archive.
8990 The fields here may contain variable references - their
8991 values will be substituted by
8992 <prgn>dpkg-gencontrol</prgn>, <prgn>dpkg-genchanges</prgn>
8993 or <prgn>dpkg-source</prgn> when they generate output
8994 control files. See <ref id="pkg-srcsubstvars"> for details.
8997 <p> <sect2><heading>User-defined fields
9001 Additional user-defined fields may be added to the
9002 source package control file. Such fields will be
9003 ignored, and not copied to (for example) binary or
9004 source package control files or upload control files.
9008 If you wish to add additional unsupported fields to
9009 these output files you should use the mechanism
9014 Fields in the main source control information file with
9015 names starting <tt>X</tt>, followed by one or more of
9016 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
9017 be copied to the output files. Only the part of the
9018 field name after the hyphen will be used in the output
9019 file. Where the letter <tt>B</tt> is used the field
9020 will appear in binary package control files, where the
9021 letter <tt>S</tt> is used in source package control
9022 files and where <tt>C</tt> is used in upload control
9023 (<tt>.changes</tt>) files.
9027 For example, if the main source information control file
9030 XBS-Comment: I stand between the candle and the star.
9032 then the binary and source package control files will contain the
9035 Comment: I stand between the candle and the star.
9042 <sect1 id="pkg-dpkgchangelog"><heading><file>debian/changelog</file>
9046 This file records the changes to the Debian-specific parts of the
9050 Though there is nothing stopping an author who is also
9051 the Debian maintainer from using it for all their
9052 changes, it will have to be renamed if the Debian and
9053 upstream maintainers become different
9060 It has a special format which allows the package building
9061 tools to discover which version of the package is being
9062 built and find out other release-specific information.
9066 That format is a series of entries like this:
9068 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
9070 * <var>change details</var>
9071 <var>more change details</var>
9072 * <var>even more change details</var>
9074 -- <var>maintainer name and email address</var> <var>date</var>
9079 <var>package</var> and <var>version</var> are the source
9080 package name and version number.
9084 <var>distribution(s)</var> lists the distributions where
9085 this version should be installed when it is uploaded - it
9086 is copied to the <tt>Distribution</tt> field in the
9087 <tt>.changes</tt> file. See <ref id="pkg-f-Distribution">.
9091 <var>urgency</var> is the value for the <tt>Urgency</tt>
9092 field in the <file>.changes</file> file for the upload. See
9093 <ref id="pkg-f-Urgency">. It is not possible to specify an
9094 urgency containing commas; commas are used to separate
9095 <tt><var>keyword</var>=<var>value</var></tt> settings in
9096 the <prgn>dpkg</prgn> changelog format (though there is
9097 currently only one useful <var>keyword</var>,
9102 The change details may in fact be any series of lines
9103 starting with at least two spaces, but conventionally each
9104 change starts with an asterisk and a separating space and
9105 continuation lines are indented so as to bring them in
9106 line with the start of the text above. Blank lines may be
9107 used here to separate groups of changes, if desired.
9111 The maintainer name and email address should <em>not</em>
9112 necessarily be those of the usual package maintainer.
9113 They should be the details of the person doing
9114 <em>this</em> version. The information here will be
9115 copied to the <file>.changes</file> file, and then later used
9116 to send an acknowledgement when the upload has been
9121 The <var>date</var> should be in RFC822 format
9124 This is generated by the <prgn>822-date</prgn>
9127 </footnote>; it should include the timezone specified
9128 numerically, with the timezone name or abbreviation
9129 optionally present as a comment.
9133 The first `title' line with the package name should start
9134 at the left hand margin; the `trailer' line with the
9135 maintainer and date details should be preceded by exactly
9136 one space. The maintainer details and the date must be
9137 separated by exactly two spaces.
9141 An Emacs mode for editing this format is available: it is
9142 called <tt>debian-changelog-mode</tt>. You can have this
9143 mode selected automatically when you edit a Debian
9144 changelog by adding a local variables clause to the end of
9148 <sect2><heading>Defining alternative changelog formats
9152 It is possible to use a different format to the standard
9153 one, by providing a parser for the format you wish to
9158 In order to have <tt>dpkg-parsechangelog</tt> run your
9159 parser, you must include a line within the last 40 lines
9160 of your file matching the Perl regular expression:
9161 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9162 parentheses should be the name of the format. For
9163 example, you might say:
9165 @@@ changelog-format: joebloggs @@@
9167 Changelog format names are non-empty strings of alphanumerics.
9171 If such a line exists then <tt>dpkg-parsechangelog</tt>
9172 will look for the parser as
9173 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9175 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9176 it is an error for it not to find it, or for it not to
9177 be an executable program. The default changelog format
9178 is <tt>dpkg</tt>, and a parser for it is provided with
9179 the <tt>dpkg</tt> package.
9183 The parser will be invoked with the changelog open on
9184 standard input at the start of the file. It should read
9185 the file (it may seek if it wishes) to determine the
9186 information required and return the parsed information
9187 to standard output in the form of a series of control
9188 fields in the standard format. By default it should
9189 return information about only the most recent version in
9190 the changelog; it should accept a
9191 <tt>-v<var>version</var></tt> option to return changes
9192 information from all versions present <em>strictly
9193 after</em> <var>version</var>, and it should then be an
9194 error for <var>version</var> not to be present in the
9200 <list compact="compact">
9202 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9205 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
9209 <qref id="pkg-f-Distribution"><tt>Distribution</tt></qref>
9214 <p><qref id="pkg-f-Urgency"><tt>Urgency</tt></qref> (mandatory)</p>
9218 <qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref>
9223 <p><qref id="pkg-f-Date"><tt>Date</tt></qref></p>
9227 <qref id="pkg-f-Changes"><tt>Changes</tt></qref>
9234 If several versions are being returned (due to the use
9235 of <tt>-v</tt>), the urgency value should be of the
9236 highest urgency code listed at the start of any of the
9237 versions requested followed by the concatenated
9238 (space-separated) comments from all the versions
9239 requested; the maintainer, version, distribution and
9240 date should always be from the most recent version.
9244 For the format of the <tt>Changes</tt> field see <ref
9245 id="pkg-f-Changes">.
9249 If the changelog format which is being parsed always or
9250 almost always leaves a blank line between individual
9251 change notes these blank lines should be stripped out,
9252 so as to make the resulting output compact.
9256 If the changelog format does not contain date or package
9257 name information this information should be omitted from
9258 the output. The parser should not attempt to synthesise
9259 it or find it from other sources.
9263 If the changelog does not have the expected format the
9264 parser should exit with a nonzero exit status, rather
9265 than trying to muddle through and possibly generating
9270 A changelog parser may not interact with the user at
9274 <sect1 id="pkg-srcsubstvars"><heading><file>debian/substvars</file>
9275 and variable substitutions
9279 When <prgn>dpkg-gencontrol</prgn>,
9280 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
9281 generate control files they do variable substitutions on
9282 their output just before writing it. Variable
9283 substitutions have the form
9284 <tt>${<var>variable-name</var>}</tt>. The optional file
9285 <file>debian/substvars</file> contains variable substitutions
9286 to be used; variables can also be set directly from
9287 <file>debian/rules</file> using the <tt>-V</tt> option to the
9288 source packaging commands, and certain predefined
9289 variables are available.
9293 The is usually generated and modified dynamically by
9294 <file>debian/rules</file> targets; in this case it must be
9295 removed by the <tt>clean</tt> target.
9299 See <manref name="dpkg-source" section="1"> for full
9300 details about source variable substitutions, including the
9301 format of <file>debian/substvars</file>.</p>
9304 <sect1><heading><file>debian/files</file>
9308 This file is not a permanent part of the source tree; it
9309 is used while building packages to record which files are
9310 being generated. <prgn>dpkg-genchanges</prgn> uses it
9311 when it generates a <file>.changes</file> file.
9315 It should not exist in a shipped source package, and so it
9316 (and any backup files or temporary files such as
9317 <file>files.new</file>
9320 <file>files.new</file> is used as a temporary file by
9321 <prgn>dpkg-gencontrol</prgn> and
9322 <prgn>dpkg-distaddfile</prgn> - they write a new
9323 version of <file>files</file> here before renaming it,
9324 to avoid leaving a corrupted copy if an error
9327 </footnote>) should be removed by the
9328 <tt>clean</tt> target. It may also be wise to
9329 ensure a fresh start by emptying or removing it at the
9330 start of the <tt>binary</tt> target.
9334 <prgn>dpkg-gencontrol</prgn> adds an entry to this file
9335 for the <file>.deb</file> file that will be created by
9336 <prgn>dpkg-deb</prgn> from the control file that it
9337 generates, so for most packages all that needs to be done
9338 with this file is to delete it in <tt>clean</tt>.
9342 If a package upload includes files besides the source
9343 package and any binary packages whose control files were
9344 made with <prgn>dpkg-gencontrol</prgn> then they should be
9345 placed in the parent of the package's top-level directory
9346 and <prgn>dpkg-distaddfile</prgn> should be called to add
9347 the file to the list in <file>debian/files</file>.</p>
9350 <sect1><heading><file>debian/tmp</file>
9354 This is the canonical temporary location for the
9355 construction of binary packages by the <tt>binary</tt>
9356 target. The directory <file>tmp</file> serves as the root of
9357 the filesystem tree as it is being constructed (for
9358 example, by using the package's upstream makefiles install
9359 targets and redirecting the output there), and it also
9360 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9361 id="pkg-bincreating">.
9365 If several binary packages are generated from the same
9366 source tree it is usual to use several
9367 <file>debian/tmp<var>something</var></file> directories, for
9368 example <file>tmp-a</file> or <file>tmp-doc</file>.
9372 Whatever <file>tmp</file> directories are created and used by
9373 <tt>binary</tt> must of course be removed by the
9374 <tt>clean</tt> target.</p></sect1>
9378 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9382 As it exists on the FTP site, a Debian source package
9383 consists of three related files. You must have the right
9384 versions of all three to be able to use them.
9389 <tag>Debian source control file - <tt>.dsc</tt></tag>
9393 This file contains a series of fields, identified and
9394 separated just like the fields in the control file of
9395 a binary package. The fields are listed below; their
9396 syntax is described above, in <ref id="pkg-controlfields">.
9397 <list compact="compact">
9399 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9402 <p><qref id="versions"><tt>Version</tt></qref></p>
9405 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
9408 <p><qref id="pkg-f-Binary"><tt>Binary</tt></qref></p>
9411 <p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref></p>
9415 <qref id="relationships"><tt>Build-Depends</tt> et
9416 al.</qref> (source package interrelationships)
9421 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref></p>
9424 <p><qref id="pkg-f-Files"><tt>Files</tt></qref></p>
9429 The source package control file is generated by
9430 <prgn>dpkg-source</prgn> when it builds the source
9431 archive, from other files in the source package,
9432 described above. When unpacking it is checked against
9433 the files and directories in the other parts of the
9434 source package, as described below.</p>
9438 Original source archive -
9440 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9447 This is a compressed (with <tt>gzip -9</tt>)
9448 <prgn>tar</prgn> file containing the source code from
9449 the upstream authors of the program. The tarfile
9450 unpacks into a directory
9451 <file><var>package</var>-<var>upstream-version</var>.orig</file>,
9452 and does not contain files anywhere other than in
9453 there or in its subdirectories.</p>
9457 Debianisation diff -
9459 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9465 This is a unified context diff (<tt>diff -u</tt>)
9466 giving the changes which are required to turn the
9467 original source into the Debian source. These changes
9468 may only include editing and creating plain files.
9469 The permissions of files, the targets of symbolic
9470 links and the characteristics of special files or
9471 pipes may not be changed and no files may be removed
9476 All the directories in the diff must exist, except the
9477 <file>debian</file> subdirectory of the top of the source
9478 tree, which will be created by
9479 <prgn>dpkg-source</prgn> if necessary when unpacking.
9483 The <prgn>dpkg-source</prgn> program will
9484 automatically make the <file>debian/rules</file> file
9485 executable (see below).</p></item>
9490 If there is no original source code - for example, if the
9491 package is specially prepared for Debian or the Debian
9492 maintainer is the same as the upstream maintainer - the
9493 format is slightly different: then there is no diff, and the
9495 <file><var>package</var>_<var>version</var>.tar.gz</file> and
9496 contains a directory
9497 <file><var>package</var>-<var>version</var></file>.
9501 <sect><heading>Unpacking a Debian source package without
9502 <prgn>dpkg-source</prgn>
9506 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9507 Debian source package. However, if it is not available it
9508 is possible to unpack a Debian source archive as follows:
9509 <enumlist compact="compact">
9512 Untar the tarfile, which will create a <file>.orig</file>
9516 <p>Rename the <file>.orig</file> directory to
9517 <file><var>package</var>-<var>version</var></file>.</p>
9521 Create the subdirectory <file>debian</file> at the top of
9522 the source tree.</p>
9524 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9526 <item><p>Untar the tarfile again if you want a copy of the original
9527 source code alongside the Debianised version.</p>
9532 It is not possible to generate a valid Debian source archive
9533 without using <prgn>dpkg-source</prgn>. In particular,
9534 attempting to use <prgn>diff</prgn> directly to generate the
9535 <file>.diff.gz</file> file will not work.
9538 <sect1><heading>Restrictions on objects in source packages
9542 The source package may not contain any hard links
9545 This is not currently detected when building source
9546 packages, but only when extracting
9552 Hard links may be permitted at some point in the
9553 future, but would require a fair amount of
9556 </footnote>, device special files, sockets or setuid or
9560 Setgid directories are allowed.
9566 The source packaging tools manage the changes between the
9567 original and Debianised source using <prgn>diff</prgn> and
9568 <prgn>patch</prgn>. Turning the original source tree as
9569 included in the <file>.orig.tar.gz</file> into the debianised
9570 source must not involve any changes which cannot be
9571 handled by these tools. Problematic changes which cause
9572 <prgn>dpkg-source</prgn> to halt with an error when
9573 building the source package are:
9574 <list compact="compact">
9575 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9577 <item><p>Changing the targets of symbolic links.</p>
9579 <item><p>Creating directories, other than <file>debian</file>.</p>
9581 <item><p>Changes to the contents of binary files.</p></item>
9582 </list> Changes which cause <prgn>dpkg-source</prgn> to
9583 print a warning but continue anyway are:
9584 <list compact="compact">
9587 Removing files, directories or symlinks.
9590 Renaming a file is not treated specially - it is
9591 seen as the removal of the old file (which
9592 generates a warning, but is otherwise ignored),
9593 and the creation of the new
9600 Changed text files which are missing the usual final
9601 newline (either in the original or the modified
9606 Changes which are not represented, but which are not detected by
9607 <prgn>dpkg-source</prgn>, are:
9608 <list compact="compact">
9609 <item><p>Changing the permissions of files (other than
9610 <file>debian/rules</file>) and directories.</p></item>
9615 The <file>debian</file> directory and <file>debian/rules</file>
9616 are handled specially by <prgn>dpkg-source</prgn> - before
9617 applying the changes it will create the <file>debian</file>
9618 directory, and afterwards it will make
9619 <file>debian/rules</file> world-exectuable.
9625 <appendix id="pkg-controlfields"><heading>Control files and their
9626 fields (from old Packaging Manual)
9630 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9631 data in a common format, known as control files. Binary and
9632 source packages have control data as do the <file>.changes</file>
9633 files which control the installation of uploaded files, and
9634 <prgn>dpkg</prgn>'s internal databases are in a similar
9638 <sect><heading>Syntax of control files
9642 A file consists of one or more paragraphs of fields. The
9643 paragraphs are separated by blank lines. Some control files
9644 only allow one paragraph; others allow several, in which
9645 case each paragraph often refers to a different package.
9649 Each paragraph is a series of fields and values; each field
9650 consists of a name, followed by a colon and the value. It
9651 ends at the end of the line. Horizontal whitespace (spaces
9652 and tabs) may occur before or after the value and is ignored
9653 there; it is conventional to put a single space after the
9658 Some fields' values may span several lines; in this case
9659 each continuation line <em>must</em> start with a space or
9660 tab. Any trailing spaces or tabs at the end of individual
9661 lines of a field value are ignored.
9665 Except where otherwise stated only a single line of data is
9666 allowed and whitespace is not significant in a field body.
9667 Whitespace may never appear inside names (of packages,
9668 architectures, files or anything else), version numbers or
9669 in between the characters of multi-character version
9674 Field names are not case-sensitive, but it is usual to
9675 capitalise the field names using mixed case as shown below.
9679 Blank lines, or lines consisting only of spaces and tabs,
9680 are not allowed within field values or between fields - that
9681 would mean a new paragraph.
9685 It is important to note that there are several fields which
9686 are optional as far as <prgn>dpkg</prgn> and the related
9687 tools are concerned, but which must appear in every Debian
9688 package, or whose omission may cause problems. When writing
9689 the control files for Debian packages you <em>must</em> read
9690 the Debian policy manual in conjuction with the details
9691 below and the list of fields for the particular file.</p>
9694 <sect><heading>List of fields
9697 <sect1 id="pkg-f-Package"><heading><tt>Package</tt>
9701 The name of the binary package. Package names consist of
9702 the alphanumerics and <tt>+</tt> <tt>-</tt> <tt>.</tt>
9703 (plus, minus and full stop).
9706 The characters <tt>@</tt> <tt>:</tt> <tt>=</tt>
9707 <tt>%</tt> <tt>_</tt> (at, colon, equals, percent
9708 and underscore) used to be legal and are still
9709 accepted when found in a package file, but may not be
9710 used in new packages
9716 They must be at least two characters and must start with
9717 an alphanumeric. In current versions of dpkg they are
9718 sort of case-sensitive<footnote><p>This is a
9719 bug.</p></footnote>; use lowercase package names unless
9720 the package you're building (or referring to, in other
9721 fields) is already using uppercase.</p>
9724 <sect1 id="pkg-f-Version"><heading><tt>Version</tt>
9728 This lists the source or binary package's version number -
9729 see <ref id="versions">.
9734 <sect1 id="pkg-f-Architecture"><heading><tt>Architecture</tt>
9738 This is the architecture string; it is a single word for
9739 the Debian architecture.
9743 <prgn>dpkg</prgn> will check the declared architecture of
9744 a binary package against its own compiled-in value before
9749 The special value <tt>all</tt> indicates that the package
9750 is architecture-independent.
9754 In the main <file>debian/control</file> file in the source
9755 package, or in the source package control file
9756 <file>.dsc</file>, a list of architectures (separated by
9757 spaces) is also allowed, as is the special value
9758 <tt>any</tt>. A list indicates that the source will build
9759 an architecture-dependent package, and will only work
9760 correctly on the listed architectures. <tt>any</tt>
9761 indicates that though the source package isn't dependent
9762 on any particular architecture and should compile fine on
9763 any one, the binary package(s) produced are not
9764 architecture-independent but will instead be specific to
9765 whatever the current build architecture is.
9769 In a <file>.changes</file> file the <tt>Architecture</tt>
9770 field lists the architecture(s) of the package(s)
9771 currently being uploaded. This will be a list; if the
9772 source for the package is being uploaded too the special
9773 entry <tt>source</tt> is also present.
9777 See <ref id="pkg-debianrules"> for information how to get the
9778 architecture for the build process.
9782 <sect1 id="pkg-f-Maintainer"><heading><tt>Maintainer</tt>
9786 The package maintainer's name and email address. The name
9787 should come first, then the email address inside angle
9788 brackets <tt><></tt> (in RFC822 format).
9792 If the maintainer's name contains a full stop then the
9793 whole field will not work directly as an email address due
9794 to a misfeature in the syntax specified in RFC822; a
9795 program using this field as an address must check for this
9796 and correct the problem if necessary (for example by
9797 putting the name in round brackets and moving it to the
9798 end, and bringing the email address forward).
9802 In a <file>.changes</file> file or parsed changelog data this
9803 contains the name and email address of the person
9804 responsible for the particular version in question - this
9805 may not be the package's usual maintainer.
9809 This field is usually optional in as far as the
9810 <prgn>dpkg</prgn> are concerned, but its absence when
9811 building packages usually generates a warning.</p>
9814 <sect1 id="pkg-f-Source"><heading><tt>Source</tt>
9818 This field identifies the source package name.
9822 In a main source control information or a
9823 <file>.changes</file> or <file>.dsc</file> file or parsed
9824 changelog data this may contain only the name of the
9829 In the control file of a binary package (or in a
9830 <file>Packages</file> file) it may be followed by a version
9831 number in parentheses.
9834 It is usual to leave a space after the package name if
9835 a version number is specified.
9837 </footnote> This version number may be omitted (and is, by
9838 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
9839 the <tt>Version</tt> field of the binary package in
9840 question. The field itself may be omitted from a binary
9841 package control file when the source package has the same
9842 name and version as the binary package.
9846 <sect1><heading>Package interrelationship fields:
9847 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
9848 <tt>Recommends</tt> <tt>Suggests</tt>, <tt>Conflicts</tt>,
9849 <tt>Provides</tt>, <tt>Replaces</tt>
9853 These fields describe the package's relationships with
9854 other packages. Their syntax and semantics are described
9855 in <ref id="relationships">.</p>
9858 <sect1 id="pkg-f-Description"><heading><tt>Description</tt>
9862 In a binary package <tt>Packages</tt> file or main source
9863 control file this field contains a description of the
9864 binary package, in a special format. See <ref
9865 id="descriptions"> for details.
9869 In a <file>.changes</file> file it contains a summary of the
9870 descriptions for the packages being uploaded. The part of
9871 the field before the first newline is empty; thereafter
9872 each line has the name of a binary package and the summary
9873 description line from that binary package. Each line is
9874 indented by one space.</p>
9877 <sect1 id="pkg-f-Essential"><heading><tt>Essential</tt>
9881 This is a boolean field which may occur only in the
9882 control file of a binary package (or in the
9883 <file>Packages</file> file) or in a per-package fields
9884 paragraph of a main source control data file.
9888 If set to <tt>yes</tt> then <prgn>dpkg</prgn> and
9889 <prgn>dselect</prgn> will refuse to remove the package
9890 (though it can be upgraded and/or replaced). The other
9891 possible value is <tt>no</tt>, which is the same as not
9892 having the field at all.</p>
9895 <sect1 id="pkg-f-classification"><heading><tt>Section</tt> and
9900 These two fields classify the package. The
9901 <tt>Priority</tt> represents how important that it is that
9902 the user have it installed; the <tt>Section</tt>
9903 represents an application area into which the package has
9908 When they appear in the <file>debian/control</file> file these
9909 fields give values for the section and priority subfields
9910 of the <tt>Files</tt> field of the <file>.changes</file> file,
9911 and give defaults for the section and priority of the
9916 The section and priority are represented, though not as
9917 separate fields, in the information for each file in the
9918 <qref id="pkg-f-Files"><tt>-File</tt></qref>field of a
9919 <file>.changes</file> file. The section value in a
9920 <file>.changes</file> file is used to decide where to install
9921 a package in the FTP archive.
9925 These fields are not used by by <prgn>dpkg</prgn> proper,
9926 but by <prgn>dselect</prgn> when it sorts packages and
9927 selects defaults. See the Debian policy manual for the
9928 priorities in use and the criteria for selecting the
9929 priority for a Debian package, and look at the Debian FTP
9930 archive for a list of currently in-use priorities.
9934 These fields may appear in binary package control files,
9935 in which case they provide a default value in case the
9936 <file>Packages</file> files are missing the information.
9937 <prgn>dpkg</prgn> and <prgn>dselect</prgn> will only use
9938 the value from a <file>.deb</file> file if they have no other
9939 information; a value listed in a <file>Packages</file> file
9940 will always take precedence. By default
9941 <prgn>dpkg-gencontrol</prgn> does not include the section
9942 and priority in the control file of a binary package - use
9943 the <tt>-isp</tt>, <tt>-is</tt> or <tt>-ip</tt> options to
9944 achieve this effect.</p>
9947 <sect1 id="pkg-f-Binary"><heading><tt>Binary</tt>
9951 This field is a list of binary packages.
9955 When it appears in the <file>.dsc</file> file it is the list
9956 of binary packages which a source package can produce. It
9957 does not necessarily produce all of these binary packages
9958 for every architecture. The source control file doesn't
9959 contain details of which architectures are appropriate for
9960 which of the binary packages.
9964 When it appears in a <file>.changes</file> file it lists the
9965 names of the binary packages actually being uploaded.
9969 The syntax is a list of binary packages separated by
9973 A space after each comma is conventional.
9975 </footnote> Currently the packages must be separated using
9976 only spaces in the <file>.changes</file> file.</p>
9979 <sect1 id="pkg-f-Installed-Size"><heading><tt>Installed-Size</tt>
9983 This field appears in the control files of binary
9984 packages, and in the <file>Packages</file> files. It gives
9985 the total amount of disk space required to install the
9990 The disk space is represented in kilobytes as a simple
9994 <sect1 id="pkg-f-Files"><heading><tt>Files</tt>
9998 This field contains a list of files with information about
9999 each one. The exact information and syntax varies with
10000 the context. In all cases the the part of the field
10001 contents on the same line as the field name is empty. The
10002 remainder of the field is one line per file, each line
10003 being indented by one space and containing a number of
10004 sub-fields separated by spaces.
10008 In the <file>.dsc</file> (Debian source control) file each
10009 line contains the MD5 checksum, size and filename of the
10010 tarfile and (if applicable) diff file which make up the
10011 remainder of the source package.
10014 That is, the parts which are not the
10017 </footnote> The exact forms of the filenames are described
10018 in <ref id="pkg-sourcearchives">.
10022 In the <file>.changes</file> file this contains one line per
10023 file being uploaded. Each line contains the MD5 checksum,
10024 size, section and priority and the filename. The section
10025 and priority are the values of the corresponding fields in
10026 the main source control file - see <ref
10027 id="pkg-f-classification">. If no section or priority is
10028 specified then <tt>-</tt> should be used, though section
10029 and priority values must be specified for new packages to
10030 be installed properly.
10034 The special value <tt>byhand</tt> for the section in a
10035 <tt>.changes</tt> file indicates that the file in question
10036 is not an ordinary package file and must by installed by
10037 hand by the distribution maintainers. If the section is
10038 <tt>byhand</tt> the priority should be <tt>-</tt>.
10042 If a new Debian revision of a package is being shipped and
10043 no new original source archive is being distributed the
10044 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
10045 entry for the original source archive
10046 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
10047 but the <file>.changes</file> file should leave it out. In
10048 this case the original source archive on the distribution
10049 site must match exactly, byte-for-byte, the original
10050 source archive which was used to generate the
10051 <file>.dsc</file> file and diff which are being uploaded.</p>
10056 id="pkg-f-Standards-Version"><heading><tt>Standards-Version</tt>
10060 The most recent version of the standards (the
10061 <prgn>dpkg</prgn> programmers' and policy manuals and
10062 associated texts) with which the package complies. This
10063 is updated manually when editing the source package to
10064 conform to newer standards; it can sometimes be used to
10065 tell when a package needs attention.
10069 Its format is the same as that of a version number except
10070 that no epoch or Debian revision is allowed - see <ref
10071 id="versions">.</p>
10075 <sect1 id="pkg-f-Distribution"><heading><tt>Distribution</tt>
10079 In a <file>.changes</file> file or parsed changelog output
10080 this contains the (space-separated) name(s) of the
10081 distribution(s) where this version of the package should
10082 be or was installed. Distribution names follow the rules
10083 for package names. (See <ref id="pkg-f-Package">).
10087 Current distribution values are:
10089 <tag><em>stable</em></tag>
10092 This is the current `released' version of Debian
10093 GNU/Linux. A new version is released approximately
10094 every 3 months after the <em>development</em> code has
10095 been <em>frozen</em> for a month of testing. Once the
10096 distribution is <em>stable</em> only major bug fixes
10097 are allowed. When changes are made to this
10098 distribution, the release number is increased
10099 (for example: 1.2r1 becomes 1.2r2 then 1.2r3, etc).
10103 <tag><em>unstable</em></tag>
10106 This distribution value refers to the
10107 <em>developmental</em> part of the Debian distribution
10108 tree. New packages, new upstream versions of packages
10109 and bug fixes go into the <em>unstable</em> directory
10110 tree. Download from this distribution at your own
10114 <tag><em>contrib</em></tag>
10117 The packages with this distribution value do not meet
10118 the criteria for inclusion in the main Debian
10119 distribution as defined by the Policy Manual, but meet
10120 the criteria for the <em>contrib</em>
10121 Distribution. There is currently no distinction
10122 between stable and unstable packages in the
10123 <em>contrib</em> or <em>non-free</em>
10124 distributions. Use your best judgement in downloading
10125 from this Distribution.</p>
10128 <tag><em>non-free</em></tag>
10131 Like the packages in the <em>contrib</em> seciton,
10132 the packages in <em>non-free</em> do not meet the
10133 criteria for inclusion in the main Debian distribution
10134 as defined by the Policy Manual. Again, use your best
10135 judgement in downloading from this Distribution.</p>
10137 <tag><em>experimental</em></tag>
10140 The packages with this distribution value are deemed
10141 by their maintainers to be high risk. Oftentimes they
10142 represent early beta or developmental packages from
10143 various sources that the maintainers want people to
10144 try, but are not ready to be a part of the other parts
10145 of the Debian distribution tree. Download at your own
10149 <tag><em>frozen</em></tag>
10152 From time to time, (currently, every 3 months) the
10153 <em>unstable</em> distribution enters a state of
10154 `code-freeze' in anticipation of release as a
10155 <em>stable</em> version. During this period of testing
10156 (usually 4 weeks) only fixes for existing or
10157 newly-discovered bugs will be allowed.
10160 </taglist> You should list <em>all</em> distributions that
10161 the package should be installed into. Except in unusual
10162 circumstances, installations to <em>stable</em> should also
10163 go into <em>frozen</em> (if it exists) and
10164 <em>unstable</em>. Likewise, installations into
10165 <em>frozen</em> should also go into <em>unstable</em>.</p>
10168 <sect1 id="pkg-f-Urgency"><heading><tt>Urgency</tt>
10172 This is a description of how important it is to upgrade to
10173 this version from previous ones. It consists of a single
10174 keyword usually taking one of the values <tt>LOW</tt>,
10175 <tt>MEDIUM</tt> or <tt>HIGH</tt>) followed by an optional
10176 commentary (separated by a space) which is usually in
10177 parentheses. For example:
10179 Urgency: LOW (HIGH for diversions users)
10184 This field appears in the <file>.changes</file> file and in
10185 parsed changelogs; its value appears as the value of the
10186 <tt>urgency</tt> attribute in a <prgn>dpkg</prgn>-style
10187 changelog (see <ref id="pkg-dpkgchangelog">).
10191 Urgency keywords are not case-sensitive.</p>
10194 <sect1 id="pkg-f-Date"><heading><tt>Date</tt>
10198 In <tt>.changes</tt> files and parsed changelogs, this
10199 gives the date the package was built or last edited.</p>
10202 <sect1 id="pkg-f-Format"><heading><tt>Format</tt>
10206 This field occurs in <file>.changes</file> files, and
10207 specifies a format revision for the file. The format
10208 described here is version <tt>1.5</tt>. The syntax of the
10209 format value is the same as that of a package version
10210 number except that no epoch or Debian revision is allowed
10211 - see <ref id="versions">.</p>
10214 <sect1 id="pkg-f-Changes"><heading><tt>Changes</tt>
10218 In a <file>.changes</file> file or parsed changelog this field
10219 contains the human-readable changes data, describing the
10220 differences between the last version and the current one.
10224 There should be nothing in this field before the first
10225 newline; all the subsequent lines must be indented by at
10226 least one space; blank lines must be represented by a line
10227 consiting only of a space and a full stop.
10231 Each version's change information should be preceded by a
10232 `title' line giving at least the version, distribution(s)
10233 and urgency, in a human-readable way.
10237 If data from several versions is being returned the entry
10238 for the most recent version should be returned first, and
10239 entries should be separated by the representation of a
10240 blank line (the `title' line may also be followed by the
10241 representation of blank line).</p>
10244 <sect1 id="pkg-f-Filename"><heading><tt>Filename</tt> and
10245 <tt>MSDOS-Filename</tt>
10249 These fields in <tt>Packages</tt> files give the
10250 filename(s) of (the parts of) a package in the
10251 distribution directories, relative to the root of the
10252 Debian hierarchy. If the package has been split into
10253 several parts the parts are all listed in order, separated
10257 <sect1 id="pkg-f-Size"><heading><tt>Size</tt> and <tt>MD5sum</tt>
10261 These fields in <file>Packages</file> files give the size (in
10262 bytes, expressed in decimal) and MD5 checksum of the
10263 file(s) which make(s) up a binary package in the
10264 distribution. If the package is split into several parts
10265 the values for the parts are listed in order, separated by
10269 <sect1 id="pkg-f-Status"><heading><tt>Status</tt>
10273 This field in <prgn>dpkg</prgn>'s status file records
10274 whether the user wants a package installed, removed or
10275 left alone, whether it is broken (requiring
10276 reinstallation) or not and what its current state on the
10277 system is. Each of these pieces of information is a
10281 <sect1 id="pkg-f-Config-Version"><heading><tt>Config-Version</tt>
10285 If a package is not installed or not configured, this
10286 field in <prgn>dpkg</prgn>'s status file records the last
10287 version of the package which was successfully
10291 <sect1 id="pkg-f-Conffiles"><heading><tt>Conffiles</tt>
10295 This field in <prgn>dpkg</prgn>'s status file contains
10296 information about the automatically-managed configuration
10297 files held by a package. This field should <em>not</em>
10298 appear anywhere in a package!</p>
10301 <sect1><heading>Obsolete fields
10305 These are still recognised by <prgn>dpkg</prgn> but should
10306 not appear anywhere any more.
10307 <taglist compact="compact">
10309 <tag><tt>Revision</tt></tag>
10310 <tag><tt>Package-Revision</tt></tag>
10311 <tag><tt>Package_Revision</tt></tag>
10314 The Debian revision part of the package version was
10315 at one point in a separate control file field. This
10316 field went through several names.</p>
10319 <tag><tt>Recommended</tt></tag>
10320 <item><p>Old name for <tt>Recommends</tt></p>
10323 <tag><tt>Optional</tt></tag>
10324 <item><p>Old name for <tt>Suggests</tt>.</p>
10326 <tag><tt>Class</tt></tag>
10327 <item><p>Old name for <tt>Priority</tt>.</p>
10335 <appendix id="pkg-conffiles"><heading>Configuration file handling
10336 (from old Packaging Manual)
10340 <prgn>dpkg</prgn> can do a certain amount of automatic
10341 handling of package configuration files.
10345 Whether this mechanism is appropriate depends on a number of
10346 factors, but basically there are two approaches to any
10347 particular configuration file.
10351 The easy method is to ship a best-effort configuration in the
10352 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10353 handle updates. If the user is unlikely to want to edit the
10354 file, but you need them to be able to without losing their
10355 changes, and a new package with a changed version of the file
10356 is only released infrequently, this is a good approach.
10360 The hard method is to build the configuration file from
10361 scratch in the <prgn>postinst</prgn> script, and to take the
10362 responsibility for fixing any mistakes made in earlier
10363 versions of the package automatically. This will be
10364 appropriate if the file is likely to need to be different on
10368 <sect><heading>Automatic handling of configuration files by
10373 A package may contain a control area file called
10374 <tt>conffiles</tt>. This file should be a list of filenames
10375 of configuration files needing automatic handling, separated
10376 by newlines. The filenames should be absolute pathnames,
10377 and the files referred to should actually exist in the
10382 When a package is upgraded <prgn>dpkg</prgn> will process
10383 the configuration files during the configuration stage,
10384 shortly before it runs the package's <prgn>postinst</prgn>
10389 For each file it checks to see whether the version of the
10390 file included in the package is the same as the one that was
10391 included in the last version of the package (the one that is
10392 being upgraded from); it also compares the version currently
10393 installed on the system with the one shipped with the last
10398 If neither the user nor the package maintainer has changed
10399 the file, it is left alone. If one or the other has changed
10400 their version, then the changed version is preferred - i.e.,
10401 if the user edits their file, but the package maintainer
10402 doesn't ship a different version, the user's changes will
10403 stay, silently, but if the maintainer ships a new version
10404 and the user hasn't edited it the new version will be
10405 installed (with an informative message). If both have
10406 changed their version the user is prompted about the problem
10407 and must resolve the differences themselves.
10411 The comparisons are done by calculating the MD5 message
10412 digests of the files, and storing the MD5 of the file as it
10413 was included in the most recent version of the package.
10417 When a package is installed for the first time
10418 <prgn>dpkg</prgn> will install the file that comes with it,
10419 unless that would mean overwriting a file already on the
10424 However, note that <prgn>dpkg</prgn> will <em>not</em>
10425 replace a conffile that was removed by the user (or by a
10426 script). This is necessary because with some programs a
10427 missing file produces an effect hard or impossible to
10428 achieve in another way, so that a missing file needs to be
10429 kept that way if the user did it.
10433 Note that a package should <em>not</em> modify a
10434 <prgn>dpkg</prgn>-handled conffile in its maintainer
10435 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10436 the user confusing and possibly dangerous options for
10437 conffile update when the package is upgraded.</p>
10440 <sect><heading>Fully-featured maintainer script configuration
10445 For files which contain site-specific information such as
10446 the hostname and networking details and so forth, it is
10447 better to create the file in the package's
10448 <prgn>postinst</prgn> script.
10452 This will typically involve examining the state of the rest
10453 of the system to determine values and other information, and
10454 may involve prompting the user for some information which
10455 can't be obtained some other way.
10459 When using this method there are a couple of important
10460 issues which should be considered:
10464 If you discover a bug in the program which generates the
10465 configuration file, or if the format of the file changes
10466 from one version to the next, you will have to arrange for
10467 the postinst script to do something sensible - usually this
10468 will mean editing the installed configuration file to remove
10469 the problem or change the syntax. You will have to do this
10470 very carefully, since the user may have changed the file,
10471 perhaps to fix the very problem that your script is trying
10472 to deal with - you will have to detect these situations and
10473 deal with them correctly.
10477 If you do go down this route it's probably a good idea to
10478 make the program that generates the configuration file(s) a
10479 separate program in <file>/usr/sbin</file>, by convention called
10480 <file><var>package</var>config</file> and then run that if
10481 appropriate from the post-installation script. The
10482 <tt><var>package</var>config</tt> program should not
10483 unquestioningly overwrite an existing configuration - if its
10484 mode of operation is geared towards setting up a package for
10485 the first time (rather than any arbitrary reconfiguration
10486 later) you should have it check whether the configuration
10487 already exists, and require a <tt>--force</tt> flag to
10488 overwrite it.</p></sect>
10491 <appendix id="pkg-alternatives"><heading>Alternative versions of
10492 an interface - <prgn>update-alternatives</prgn> (from old
10497 When several packages all provide different versions of the
10498 same program or file it is useful to have the system select a
10499 default, but to allow the system administrator to change it
10500 and have their decisions respected.
10504 For example, there are several versions of the <prgn>vi</prgn>
10505 editor, and there is no reason to prevent all of them from
10506 being installed at once, each under their own name
10507 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10508 Nevertheless it is desirable to have the name <tt>vi</tt>
10509 refer to something, at least by default.
10513 If all the packages involved cooperate, this can be done with
10514 <prgn>update-alternatives</prgn>.
10518 Each package provides its own version under its own name, and
10519 calls <prgn>update-alternatives</prgn> in its postinst to
10520 register its version (and again in its prerm to deregister
10525 See the manpage <manref name="update-alternatives"
10526 section="8"> for details.
10530 If <prgn>update-alternatives</prgn> does not seem appropriate
10531 you may wish to consider using diversions instead.</p>
10534 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10535 package's version of a file (from old Packaging Manual)
10539 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10540 when it reinstalls the package it belongs to, and to have it
10541 put the file from the package somewhere else instead.
10545 This can be used locally to override a package's version of a
10546 file, or by one package to override another's version (or
10547 provide a wrapper for it).
10551 Before deciding to use a diversion, read <ref
10552 id="pkg-alternatives"> to see if you really want a diversion
10553 rather than several alternative versions of a program.
10557 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10558 and updated by a special program <prgn>dpkg-divert</prgn>.
10559 Please see <manref name="dpkg-divert" section="8"> for full
10560 details of its operation.
10564 When a package wishes to divert a file from another, it should
10565 call <prgn>dpkg-divert</prgn> in its preinst to add the
10566 diversion and rename the existing file. For example,
10567 supposing that a <prgn>smailwrapper</prgn> package wishes to
10568 install a wrapper around <file>/usr/sbin/smail</file>:
10570 if [ install = "$1" ]; then
10571 dpkg-divert --package smailwrapper --add --rename \
10572 --divert /usr/sbin/smail.real /usr/sbin/smail
10574 </example> Testing <tt>$1</tt> is necessary so that the script
10575 doesn't try to add the diversion again when
10576 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10577 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10578 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10579 get installed as the true version.
10583 The postrm has to do the reverse:
10585 if [ remove = "$1" ]; then
10586 dpkg-divert --package smailwrapper --remove --rename \
10587 --divert /usr/sbin/smail.real /usr/sbin/smail
10593 Do not attempt to divert a file which is vitally important for
10594 the system's operation - when using <prgn>dpkg-divert</prgn>
10595 there is a time, after it has been diverted but before
10596 <prgn>dpkg</prgn> has installed the new version, when the file
10597 does not exist.</p>